COMMUNICATION DEVICE AND BASE STATION INVOLVED IN CELL MOBILITY PROCEDURE - Patent application

Abstract

The receiving unit receives from the source base station an initial cell configuration of at least one candidate target cell, each initial cell configuration including cell configuration parameters for each candidate target cell for performing a conditional cell mobility procedure and an execution condition for when to perform the conditional cell mobility procedure for each candidate target cell. When the execution condition is satisfied for a target cell among the at least one candidate target cell, the circuitry performs the conditional cell mobility procedure for the target cell based on the cell configuration parameters of the target cell. When the conditional cell mobility procedure between the communication device and the target cell is completed, the circuitry maintains the received initial cell configuration of the at least one candidate target cell.

Description

[Technical Field]

[0001] The present disclosure is directed to methods, apparatus, and articles in communication systems, such as 3GPP® communication systems. [Background technology]

[0002] Currently, the 3rd Generation Partnership Project (3GPP) is working on technical specifications for a new radio access technology—5G New Radio (NR), also known as fifth generation (5G) or NR, which are used interchangeably herein.

[0003] One objective is to provide a single technical framework that addresses all usage scenarios, requirements, and deployment scenarios (see, e.g., Section 6 of 3GPP TR 38.913, e.g., version 16.0.0 or version 17.0.0) including at least enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine-type communication (mMTC). For example, eMBB deployment scenarios may include indoor hotspots, dense urban, rural, urban macro, and high-speed; URLLC deployment scenarios may include industrial control systems, mobile healthcare (remote monitoring, diagnosis, and treatment), real-time control of vehicles, wide-area monitoring, and control systems for smart grids; and mMTC deployment scenarios may include scenarios with a large number of devices with non-time-critical data transfer, such as smart wearables and sensor networks. eMBB and URLLC services are similar in that they both require very high bandwidth, but URLLC services differ in that they preferably require very low latency.

[0004] A second goal is to achieve forward compatibility, which facilitates the introduction of entirely new system designs and / or new features. Summary of the Invention [Problem to be solved by the invention]

[0005] One non-limiting, exemplary embodiment facilitates providing a procedure for a communication device to perform an improved cell mobility procedure. [Means for solving the problem]

[0006] In one embodiment, the technology disclosed herein features a communications device including: a receiver that receives, from a source base station, an initial cell configuration of at least one candidate target cell, each initial cell configuration including cell configuration parameters for each candidate target cell for performing a conditional cell mobility procedure and an execution condition for when to perform the conditional cell mobility procedure for each candidate target cell; a circuit in the communications device that, when the execution condition is satisfied for a target cell among the at least one candidate target cell, performs the conditional cell mobility procedure for the target cell based on the cell configuration parameters of the target cell; and, when the conditional cell mobility procedure between the communications device and the target cell is completed, maintains the received initial cell configuration of the at least one candidate target cell.

[0007] It should be noted that the general or specific embodiments may be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any combination thereof. For example, an integrated circuit may control the processing of a communications device or a base station.

[0008] Further benefits and advantages of the disclosed embodiments and various implementations will become apparent from the specification and drawings. These benefits and / or advantages may be obtained individually by the various embodiments and features of the specification and drawings, and it is not necessary for all embodiments and features to be present in order to obtain one or more of such benefits and / or advantages. [Brief explanation of the drawings]

[0009] The following embodiments will be described in more detail with reference to the accompanying drawings. [Figure 1] FIG. 1 illustrates an example architecture of a 3GPP NR system to which the improved procedures of the present disclosure can be applied. [Figure 2] 1 is a schematic diagram illustrating the functional division between the NG Radio Access Network (NG-RAN) and the 5G Core Network (5GC), to which the improved procedures of the present disclosure may be applied; [Figure 3] 1 is a sequence diagram of a Radio Resource Control (RRC) connection setup / reconfiguration procedure to which the improved procedures of the present disclosure may be applied. [Figure 4] FIG. 1 is a schematic diagram illustrating eMBB, mMTC, and URLLC usage scenarios in which the improved procedures of the present disclosure may be applied. [Figure 5] Block diagram illustrating an example 3GPP NR system architecture for a non-roaming scenario [Figure 6] Diagram outlining the different cell types in dual connectivity [Figure 7] Signaling diagram for handover involving UE, source gNB, and target gNB [Figure 8] Diagram showing an example of a conditional handover involving a UE, a source gNB, and a target gNB [Figure 9] FIG. 1 illustrates another exemplary conditional handover. [Figure 10] FIG. 1 illustrates another exemplary conditional handover. [Figure 11] Signaling diagram for conditional PSCell change procedure [Figure 12] Signaling diagram for conditional PSCell addition procedure [Figure 13] FIG. 1 shows an exemplary simplified structure of a UE and a gNB. [Figure 14] FIG. 1 illustrates the structure of a UE according to an embodiment of the improved mobility procedure. [Figure 15] 1 is a flow diagram of UE behavior according to an embodiment of the improved mobility procedure; [Figure 16] FIG. 1 illustrates the structure of a source base station according to an embodiment of the improved mobility procedure. [Figure 17] 1 is a flow diagram of source base station behavior according to an embodiment of the improved mobility procedure; [Figure 18] FIG. 1 illustrates the structure of a target base station according to an embodiment of the improved mobility procedure. [Figure 19] 1 is a flow diagram of target base station behavior according to an embodiment of the improved mobility procedure; [Figure 20] 1 is a signaling diagram illustrating exemplary interactions between a UE, a source gNB, and a target gNB according to an embodiment of an improved mobility procedure, in particular an improved CHO procedure; [Figure 21] 1 is a signaling diagram illustrating exemplary interactions between a UE, a source gNB, and a target gNB in a first embodiment of an improved CHO procedure; [Figure 22] 1 is a signaling diagram illustrating exemplary interactions between a UE, a source gNB, and a target gNB in a second embodiment of an improved CHO procedure. [Figure 23] 10 is a signaling diagram illustrating exemplary interactions between a UE, a source gNB, and a target gNB in a third embodiment of an improved CHO procedure. [Figure 24] 1 is a signaling diagram illustrating exemplary interactions between a UE, a source gNB, and a target gNB according to an embodiment of an improved CPC procedure. [Figure 25]1 is a signaling diagram illustrating exemplary interactions between a UE, a source gNB, and a target gNB according to an embodiment of the improved CPA procedure. DETAILED DESCRIPTION OF THE INVENTION

[0010] <5G NR system architecture and protocol stack> 3GPP is working on the next release of fifth-generation cellular technology (also known simply as "5G"), which involves developing new radio access technologies operating in the frequency range up to 100 GHz. The first version of the 5G standard was completed in late 2017, allowing for the prototyping and commercial deployment of 5G NR-compliant smartphones.

[0011] In particular, the overall system architecture assumes a Next Generation Radio Access Network (NG-RAN) comprising gNBs. The gNBs provide UE-side termination of the NG radio access user plane (SDAP / PDCP / RLC / MAC / PHY) and control plane (RRC) protocols. The gNBs are interconnected via the Xn interface. The gNBs are also connected to 5GC via the Next Generation (NG) interface, more specifically to the Access and Mobility Management Function (AMF, e.g., a specific core entity that runs AMF) via the NG-C interface and to the User Plane Function (UPF, e.g., a specific core entity that runs UPF) via the NG-U interface. The NG-RAN architecture is shown in Figure 1 (see, e.g., 3GPP TS 38.300, e.g., v16.8.0, Section 4).

[0012] The NR user plane protocol stack (see, for example, Section 4.4.1 of 3GPP TS 38.300) includes the Packet Data Convergence Protocol (PDCP) sublayer (see, for example, Section 6.4 of 3GPP TS 38.300), the Radio Link Control (RLC) sublayer (see, for example, Section 6.3 of TS 38.300), and the Medium Access Control (MAC) sublayer (see, for example, Section 6.2 of TS 38.300). Furthermore, a new Access Stratum (AS) sublayer (Service Data Adaptation Protocol (SDAP)) is introduced above PDCP (see, for example, Sub-clause 6.5 of TS 38.300). NR also defines a control plane protocol stack (see, for example, Section 4.4.2 of TS 38.300). An overview of Layer 2 functions is provided in Sub-clause 6 of TS 38.300. The functions of the RRC layer are listed in sub-clause 7 of TS 38.300.

[0013] For example, the MAC layer is responsible for multiplexing logical channels and scheduling and scheduling-related functions, including handling various numerologies.

[0014] The physical layer (PHY) is responsible for, for example, coding, PHY HARQ processing, modulation, multi-antenna processing, and mapping of signals to appropriate physical time-frequency resources. It also maps transport channels to physical channels. The physical layer provides services to the MAC layer in the form of transport channels. A physical channel corresponds to a set of time-frequency resources used for transmitting a specific transport channel, and each transport channel is mapped to a corresponding physical channel. For example, the physical channels are the Physical Random Access Channel (PRACH), the Physical Uplink Shared Channel (PUSCH), and the Physical Uplink Control Channel (PUCCH) in the uplink, and the Physical Downlink Shared Channel (PDSCH), the Physical Downlink Control Channel (PDCCH), and the Physical Broadcast Channel (PBCH) in the downlink.

[0015] NR use cases / deployment scenarios include enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine Type Communication (mMTC), which have diverse requirements for data rate, latency, and coverage. For example, eMBB requires peak data rates (20 Gbps downlink, 10 Gbps uplink) and effective (user-experienced) data rates three times higher than those offered by IMT-Advanced. On the other hand, URLLC has more stringent requirements for ultra-low latency (user plane latency of 0.5 ms for both UL and DL) and high reliability (1-10 Mbps latency within 1 ms). -5Finally, mMTC preferably requires high connection density (1 million devices per square kilometer in urban environments), wide coverage in adverse environments, and ultra-long battery life (15 years) for low-cost equipment.

[0016] Therefore, OFDM numerology (e.g., subcarrier spacing, OFDM symbol length, cyclic prefix (CP) length, number of symbols per scheduling interval) suitable for one use case may not be valid for another use case. For example, low-latency services may preferably require a shorter symbol length (and therefore a larger subcarrier spacing) and / or fewer symbols per scheduling interval (i.e., TTI) than mMTC services. Furthermore, deployment scenarios with large channel delay spreads may preferably require a longer CP length than scenarios with small delay spreads. To maintain similar CP overhead, the subcarrier spacing needs to be optimized accordingly. NR may support multiple values of subcarrier spacing. Correspondingly, subcarrier spacings of 15 kHz, 30 kHz, 60 kHz, and so on are currently being considered. The symbol length T u and the subcarrier spacing Δf is given by the formula Δf=1 / T u Similar to LTE systems, the term "resource element" can be used to denote the smallest resource unit consisting of one subcarrier for the length of one OFDM / SC-FDMA symbol.

[0017] In the new radio system 5G-NR, a resource grid of subcarriers and OFDM symbols is defined for each numerology and carrier for the uplink and downlink, respectively. Each element of the resource grid is called a resource element and is identified based on its frequency index in the frequency domain and its symbol position in the time domain (see 3GPP TS 38.211, e.g., v17.1.0, e.g., Section 4). For example, downlink and uplink transmissions are organized into frames with a duration of 10 ms, and each frame consists of 10 subframes, each with a duration of 1 ms. In a 5G NR implementation, the number of consecutive OFDM symbols per subframe depends on the subcarrier spacing setting. For example, for a subcarrier spacing of 15 kHz, a subframe has 14 OFDM symbols (similar to an LTE-compatible implementation assuming a normal cyclic prefix). On the other hand, for a subcarrier spacing of 30 kHz, a subframe has two slots, each containing 14 OFDM symbols.

[0018] <Functional separation between NG-RAN and 5GC in 5G NR> Figure 2 shows the functional separation between NG-RAN and 5GC. The logical node of NG-RAN is gNB or ng-eNB. 5GC has logical nodes AMF, UPF, and SMF.

[0019] In particular, the gNB and ng-eNB host the following main functions: - Radio Resource Management functions such as Radio Bearer Control, Radio Admission Control, Connection Mobility Control, dynamic allocation (scheduling) of resources to UEs in both uplink and downlink; - IP header compression, encryption, and integrity protection of data; - AMF selection at UE attach time if routing to the AMF cannot be determined from the information provided by the UE; - Routing of user plane data towards UPF; - Routing of control plane information towards AMF; - Setting up and tearing down connections; - scheduling and sending of paging messages; - Scheduling and transmission of system broadcast information (originating from AMF or Operation, Admission, and Maintenance Function (OAM)); - Setting up measurements and reporting of measurements for mobility and scheduling; - Transport-level packet marking in the uplink; - Session management; - Network slicing support; - QoS flow management and mapping to data radio bearers; - Support for UEs in RRC_INACTIVE state; - Non-Access Stratum (NAS) message delivery functions; - Sharing of radio access networks; - Dual connectivity; - Close cooperation between NR and E-UTRA.

[0020] The Access and Mobility Management Function (AMF) hosts the following main functions: - Terminating Non-Access Stratum (NAS) signaling; - NAS signaling security; - Access Layer (AS) security controls; - 3GPP Core Network (CN) inter-node signaling for mobility between access networks; - Reachability to idle mode UEs (including control and execution of paging retransmissions); - Managing the registration area; - Support for intra-system and inter-system mobility; - Access authentication; - Access authorization, including checking roaming privileges; - Mobility management control (subscription and policy); - Network slicing support; - Session Management Function (SMF) selection.

[0021] Additionally, the User Plane Function (UPF) hosts the following main functions: - Anchor points for intra-RAT / inter-RAT mobility (if applicable); - External PDU (Protocol Data Unit) session points for interconnection with data networks; - Packet routing and forwarding; - Packet inspection and policy rule enforcement for the user plane part; - Traffic usage reporting; - uplink classifier, which supports routing of traffic flows to the data network; - Branching Point to support multi-homed PDU sessions; - QoS processing for the user plane (e.g., packet filtering, gating, UL / DL rate enforcement); - Uplink traffic validation (mapping of SDF to QoS flows); - Downlink packet buffering and triggering of downlink data notifications.

[0022] Finally, the Session Management Function (SMF) hosts the following main functions: - Session management; - IP address allocation and management for the UE; - Selection and control of the UPF; - Traffic steering setting function in the User Plane Function (UPF) for routing traffic to the appropriate destination; - Policy enforcement and QoS of the control part; - Notification of downlink data.

[0023] <Procedures for RRC connection setup and reconfiguration> Figure 3 shows some of the interactions between the UE, gNB, and AMF (5GC entity) in the NAS part when the UE transitions from RRC_IDLE to RRC_CONNECTED (see TS 38.300).

[0024] RRC is a higher layer signaling protocol used to configure the UE and the gNB. In particular, with this transition, the AMF prepares UE context data (including, for example, PDU session context, security keys, UE Radio Capabilities, UE Security Capabilities, etc.) and sends it to the gNB with an INITIAL CONTEXT SETUP REQUEST. The gNB then activates AS security together with the UE. This is done by the gNB sending a SecurityModeCommand message to the UE, and the UE responding with a SecurityModeComplete message to the gNB. The gNB then sends an RRCReconfiguration message to the UE, and upon receiving an RRCReconfigurationComplete from the UE, the gNB performs reconfiguration to set up signaling radio bearer 2 (SRB2) and data radio bearers (DRBs). For signaling-only connections, the RRCReconfiguration steps are omitted because SRB2 and DRBs are not set up. Finally, the gNB notifies the AMF that the setup procedure is complete with an INITIAL CONTEXT SETUP RESPONSE.

[0025] Therefore, the present disclosure provides a 5GC entity (e.g., AMF, SMF, etc.) that includes, in operation, a circuit for establishing a Next Generation (NG) connection with a gNodeB, and a transmitter that, in operation, transmits an initial context setup message to a gNodeB via the NG connection so that a signaling radio bearer between the gNodeB and a user equipment (UE) is set up. Specifically, the gNodeB transmits RRC signaling including a resource allocation configuration information element (IE) to the UE via the signaling radio bearer. The UE then transmits in the uplink or receives in the downlink based on the resource allocation configuration.

[0026] <IMT usage scenarios from 2020 onwards> Figure 4 shows some of the use cases for 5G NR. The 3rd Generation Partnership Project NR (3GPP NR) is considering three use cases that are expected to support a wide variety of services and applications through IMT-2020. The first phase of specifications for enhanced Mobile Broadband (eMBB) has been completed. In addition to further expanding support for eMBB, current and future research is also underway on the standardization of ultra-reliable low-latency communication (URLLC) and multiple simultaneous connections. Figure 4 shows examples of usage scenarios expected for IMT beyond 2020 (see, for example, Figure 2 in ITU-R M.20183).

[0027] URLLC use cases have stringent performance requirements for throughput, latency, and availability, and are envisioned as one of the enablers of future vertical applications, such as wireless control of industrial production and manufacturing processes, remote medical surgery, smart grid power distribution automation, and road safety. URLLC's ultra-high reliability is supported by identifying technologies that meet the requirements set by 3GPP TR 38.913v16.0.0. For NR URLLC in Release 15, a key requirement is a user-plane latency target of 0.5 ms on the uplink (UL) and 0.5 ms on the downlink (DL). A typical URLLC requirement for a single packet transmission is a block error rate (BLER) of 1E-5 for a 32-byte packet size with a user-plane latency of 1 ms.

[0028] From a physical layer perspective, reliability can be improved in many possible ways. Current reliability improvement room includes defining a separate CQI table for URLLC, a more compact DCI format, repeated transmission of PDCCH, etc. However, this room can be expanded to achieve ultra-high reliability as NR (with respect to the key requirements of NR URLLC) becomes more stable and developed. Specific use cases for NR URLLC in Release 15 include augmented reality / virtual reality (AR / VR), e-health, e-safety, and mission-critical applications.

[0029] Additionally, technology enhancements targeted by NR URLLC aim to improve latency and reliability. Technology enhancements for latency improvement include configurable numerology, non-slot-based scheduling with flexible mapping, grant-free (configurable grant) uplink, slot-level repeated transmission in the data channel, and preemption in the downlink. Preemption means that a transmission with already allocated resources is stopped and the allocated resources are used for another transmission with lower latency / higher priority requirements that are requested later. Thus, a previously allowed transmission is preempted by a later transmission. Preemption is applicable regardless of the specific service type. For example, a transmission of service type A (URLLC) can be preempted by a transmission of service type B (eMBB, etc.). Technology enhancements for reliability improvement include dedicated CQI / MCS tables for a target BLER of 1E-5.

[0030] The mMTC (Massive Machine Type Communications) use case is characterized by a very large number of connected devices that typically transmit relatively small amounts of data that are not sensitive to latency. These devices are required to be low cost and have very long battery life. From an NR perspective, using very narrow bandwidth portions is one solution that saves power and allows for long battery life from the UE perspective.

[0031] As mentioned above, the scope of reliability improvement in NR is expected to become broader. One of the key requirements for all cases, especially for URLLC and mMTC, is high or ultra-high reliability. Several mechanisms can be considered to improve reliability from the radio and network perspectives. Generally, there are two to three key areas that can help improve reliability. These areas include compact control channel information, repeated transmission of data channels / control channels, and diversity in the frequency, time, and / or spatial domains. These areas are generally applicable to reliability improvement regardless of the specific communication scenario.

[0032] Further use cases with more stringent requirements are envisioned for NR URLLC, such as factory automation, transportation, and power distribution. The stringent requirements include high reliability (10 6 level of reliability), high availability, packet sizes up to 256 bytes, time synchronization up to a few microseconds (depending on the use case, the value can be 1 microsecond or a few microseconds depending on the frequency range and low latency in the 0.5ms-1ms range (especially for targeted user plane latency of 0.5ms).

[0033] Furthermore, for NR URLLC, there may be several technical extensions from the perspective of the physical layer. These technical extensions include the extension of the PDCCH (Physical Downlink Control Channel) related to compact DCI, the repeated transmission of the PDCCH, and the increase in the monitoring of the PDCCH. Also, the extension of UCI (Uplink Control Information) is related to the extension of enhanced HARQ (Hybrid Automatic Repeat Request) and CSI feedback. There may also be an extension of the PUSCH related to mini-slot level hopping, and an extension of retransmission / repeated transmission. The term "mini-slot" refers to a transmission time interval (TTI) that contains fewer symbols than a slot (a slot contains 14 symbols).

[0034] <QoS Control> The QoS (Quality of Service) model of 5G is based on QoS flows and supports both QoS flows that require a guaranteed flow bit rate (GBR (Granteed Bit Rate) QoS flows) and QoS flows that do not require a guaranteed flow bit rate (non-GBR QoS flows). Therefore, at the NAS level, a QoS flow is the finest granularity of QoS differentiation in a PDU session. A QoS flow is identified within a PDU session by a QoS flow ID (QFI: QoS Flow ID) that is carried in an encapsulation header via the NG-U interface.

[0035] For each UE, the 5GC establishes one or more PDU sessions. For each UE, the NG-RAN establishes at least one Data Radio Bearer (DRB) for each PDU session, e.g., as shown above with reference to Figure 3. Additional DRBs for the QoS flows of that PDU session can be configured later (when this is up to the NG-RAN). The NG-RAN maps packets belonging to different PDU sessions to different DRBs. NAS-level packet filters in the UE and the 5GC associate UL packets and DL packets with QoS flows, while AS-level mapping rules in the UE and the NG-RAN associate UL QoS flows and DL QoS flows with DRBs.

[0036] Figure 5 shows the non-roaming reference architecture for 5G NR (see, for example, 3GPP TS 23.501, e.g., v16.9.0 or v17.4.0, section 4.2.3). As illustrated in Figure 4, an application function (AF), such as an external application server hosting 5G services, interacts with the 3GPP core network to provide the service. For example, it accesses a network exposure function (NEF) to support applications that affect traffic routing, and interacts with a policy framework for policy control such as QoS control (see Policy Control Function (PCF)). Based on operator deployment, application functions that are deemed trusted by the operator can interact directly with the relevant network functions. Application functions that are not authorized by the operator to directly access network functions interact with the relevant network functions using the external exposure framework via the NEF.

[0037] Figure 5 further illustrates additional functional units of the 5G architecture, namely, the Network Slice Selection Function (NSSF), the Network Repository Function (NRF), the Unified Data Management Function (UDM), the Authentication Server Function (AUSF), the Access and Mobility Management Function (AMF), the Session Management Function (SMF), and the Data Network (DN, e.g., operator-provided services, Internet access, or third-party services). All or part of the core network functions and application services may be deployed and run in a cloud computing environment.

[0038] Therefore, the present disclosure provides an application server (e.g., an AF in a 5G architecture) comprising: a transmitter that, in operation, sends a request including QoS requirements for at least one of a URLLC service, an eMBB service, and an mMTC service to at least one of 5GC functions (e.g., an NEF, an AMF, an SMF, a PCF, an UPF, etc.) to establish a PDU session including a radio bearer between a gNodeB and a UE according to the QoS requirements; and a circuit that, in operation, performs a service using the established PDU session.

[0039] <5G NR cell types> In 5G NR, there are several types of cells: PCell, SCell, PSCell, and SpCell.

[0040] The PCell is a primary cell that may be used to initiate initial access.

[0041] An SCell is a secondary cell. A UE can be configured with one or more SCells in connected mode. An SCell can be activated or deactivated, for example, depending on traffic.

[0042] PSCell is closely related to Dual Connectivity (DC). E-UTRAN supports Dual Connectivity (DC) operation, where a Multiple-Rx / Tx UE in RRC_CONNECTED can be configured to utilize radio resources provided by two different schedulers located in two nodes (master node, secondary node) connected by a non-ideal backhaul via the X2 interface. The master node provides the control plane connection to the core network. The secondary node does not have a control plane connection with the core network, but in the case of MR-DC, provides additional resources to the UE.

[0043] In dual connectivity, there are two cell groups: a Master Cell Group (MCG) and a Secondary Cell Group (SCG). The MCG may have one PCell and one or more SCells. The SCG may have one PSCell and one or more SCells. The UE performs initial access in the SCG via the PSCell. Since most signaling messages are transmitted only via the PCell and PSCell, for ease of explanation, 3GPP defines the concept of a Special cell (SpCell), which is understood as SpCell = Pcell + PSCell.

[0044] Figure 6 provides an overview of the different cell types in dual connectivity.

[0045] There is also the possibility of Multi-Radio Dual Connectivity (MR-DC), where the Master RAN Node acts as the control entity that utilizes the secondary RAN for additional data capacity. MR-DC configurations include EN-DC (E-UTRA-NR dual connectivity), NR-DC (NR dual connectivity), NGEN-DC (NG-RAN-E-UTRA dual connectivity), and NE-DC (NR-E-UTR dual connectivity).

[0046] TS 37.340 v17.1.0 defines multi-radio dual connectivity in clause 4. As shown in TS 38.300 v17.1.0 clause 4.5, conditional PSCell addition (CPA) and conditional PSCell change (CPC) are defined in TS 37.340 and are further explained below.

[0047] <Handover procedure> An exemplary simplified handover is shown in Figure 7 and briefly described below. Handover of a UE involves a source base station making a decision whether to handover the UE from a source / serving gNB to a neighboring / target gNB (target radio cell). This decision is typically made by the source gNB based on measurement results from the UE. The measurement results may be carried in one or more measurement reports, for example, as shown in the measurement report of Figure 7. The measurement reports are sent by the UE to assist the source cell in the handover procedure.

[0048] Then, a handover is prepared (preparation phase) between the two base stations involved, i.e., a source base station (herein, source gNB, which may be used interchangeably with source cell) and a target base station (herein, target gNB, which may be used interchangeably with target cell). The source gNB sends a handover request message to the target base station, and the target base station may respond with a handover request acknowledgement message to perform the preparation phase. Such a preparation phase allows neighboring cells to determine whether they have the capacity to accept additional UEs (e.g., whether to acknowledge handover) and reserve resources for the UE.

[0049] Then, in the execution phase, the UE is instructed to switch from the source cell to the target cell via a handover command message (e.g., an RRCReconfiguration message), which involves, for example, reconfiguring the UE's radio resources to establish a connection with a target base station of the target radio cell. The UE then reconfigures and connects to the new target base station accordingly, performing synchronization and (e.g., contention-free) random access procedures in the process. For example, synchronization may involve the UE acquiring synchronization signals (e.g., a Primary Synchronization Signal (PSS) and a Secondary Synchronization Signal (SSS)) that are typically used to acquire the cell identity and frame timing of the target cell, thereby achieving time and frequency synchronization. A random access procedure may be performed by the UE to, for example, acquire a timing advance value and acquire uplink resources for uplink transmission using an RAR message. The random access procedure may include, for example, transmitting a RACH preamble (e.g., a dedicated preamble (following the preamble indicated in the handover command message for contention-free RACH)), receiving a random access response message (e.g., including an uplink grant), and, as the third and final step of the random access procedure, confirming that the UE has completed reconfiguration and access to the target cell by transmitting a handover confirmation message (RRCReconfigurationComplete message) to the target gNB.

[0050] An example of such a handover procedure is defined in 3GPP technical specification TS 38.300 v17.1.0, section 9.2.3.2, for 5G NR for RRC connection mobility.

[0051] The handover command message may include information about the target cell, such as a target cell ID and setting information for enabling connection to the target cell, as well as handover acceptance conditions and handover rejection conditions.

[0052] As an exemplary and simplified overview, the RRCReconfiguration message may include one or more of the following: Target Cell ID New C-RNTI Target gNB security algorithm identifier for the selected security algorithm Dedicated RACH resources Common RACH resources ·Associating RACH resources with SSB - Target cell system information According to a more detailed and exemplary definition of the possible contents of the handover command message, 5G NR defines the RRCReconfiguration message in section 6.2.2 of 3GPP TS 38.331 v17.1.0. According to 5G, the RRCReconfiguration message is a command to modify the RRC connection. It may carry information for measurement configuration, mobility control, radio resource configuration (including radio bearers (RBs), medium access control (MAC) primary configuration and physical channel configuration), and access stratum (AS) security configuration.

[0053] <Conditional Handover - CHO> In the legacy handover procedure, the gNB is responsible for determining whether a handover should be performed. This handover procedure is a passive process that is prone to handover failure. For example, if the radio link degrades and the mobile terminal needs to send a measurement report, the measurement report may not reach the network. Or, even if it does, the network attempts to respond with a handover command that may never reach the mobile terminal because the downlink is degraded and / or the handover command is too large and requires multiple transmissions.

[0054] Conditional Handover (CHO), one of the key mobility enhancements specified by 3GPP in Rel-16, focuses on reducing the number of failures that occur during user mobility, for example, when inter-cell handovers fail or when connectivity fails before a handover (HO) is triggered. In this way, CHO improves mobility robustness for handovers. Furthermore, it can reduce signaling and handover delays. CHO can be used to change the PCell for either a UE without dual connectivity or a master cell group for a UE with dual connectivity. In dual connectivity (DC), a PCell change procedure can be performed to change the PCell of the master cell group.

[0055] Due to its usefulness, CHO is being considered in many areas where cellular communications are applied, including, for example, Mobile Broadband (MBB), Non-Terrestrial Networks (NTN), integrated access backhaul, and NR-unlicensed.

[0056] In a conditional handover, the mobile terminal receives a handover command (e.g., an RRCReconfiguration message containing conditional configuration information prepared by the target candidate cell) from the source gNB. Upon receipt, the mobile terminal stores the settings in the handover command rather than applying them immediately as in a legacy handover. Along with the handover command, the mobile terminal also receives associated conditions that are monitored by the mobile terminal. The mobile terminal only applies the stored command if the conditions are met. The mobile terminal then performs the handover and connects to the target node, similar to a normal handover.

[0057] As an example, the source gNB may be responsible for preparing the conditional handover, including execution conditions regarding when the UE should perform (i.e., trigger) the CHO, while the candidate target gNB provides the CHO configuration parameters to be forwarded by the source gNB to the mobile terminal.

[0058] An exemplary basic CHO procedure is illustrated by the signaling diagram in FIG. 8. As can be seen, the source gNB prepares CHO together with the target gNB. The target gNB provides the source gNB with corresponding target cell-specific configuration parameters. The source gNB sends a CHO command to the UE, including the target cell configuration and execution conditions for the target cell. Upon receiving the CHO command, the UE does not detach from the source gNB (unlike legacy handover); instead, the UE continues exchanging UL and DL data with the source gNB until the CHO execution conditions are met. Once the execution conditions for the target cell are met, the UE begins executing CHO (e.g., in a manner similar or equivalent to legacy handover).

[0059] According to one example, the configuration parameters of the target gNB may include one or more of the following:

[0060] Radio resource configuration of candidate target cells, such as resource blocks and physical channel configuration Security settings for candidate target cells Dual connectivity information such as master cell group information, secondary cell group information, etc. Measurement settings for candidate target cells Mobility information (including, for example, handover settings and conditional settings).

[0061] Another exemplary and simplified CHO procedure is illustrated in more detail by the signaling diagram of FIG. 9 compared to the basic signaling diagram of FIG. 8. Thereby, the source gNB prepares CHO, for example, based on measurements received from a mobile terminal. Thus, the source gNB identifies gNB1 as a potential target for CHO and sends a handover request (here, CHO Request) to the target gNB (e.g., in 5G, for example, according to TS 38.423 v17.1.0, the corresponding CHO-related IE in the Handover Request message is the IE Conditional Handover Information Request). The target gNB processes the received handover request (e.g., performs admission control), and once the target gNB grants the mobile terminal access to the cell, the target gNB sends an appropriate CHO response message (CHO ACK) to the source gNB. As an example, the shared CHO configuration can include one or more requested target cell IDs and a maximum number of CHO preparations (see Section 9.1.1.2 of TS 38.423 v17.1.0). In general, the CHO ACK message may contain the configuration information required to access the target cell (e.g. in the form of a handover request acknowledgement message, e.g. an XnAp, Xn Application Protocol, signaling message according to the 3GPP standard TS 38.423).

[0062] In this embodiment, when the source gNB receives a CHO ACK from the target cell, it determines the appropriate CHO execution conditions.

[0063] The source gNB then transmits a CHO configuration to the mobile terminal, which includes, for example, configuration information for accessing the target cell (the configuration information received by the source gNB from the target gNB) and the determined CHO execution condition, both of which are stored by the mobile terminal. Thus, the mobile terminal is provided with information necessary to perform the conditional handover. For example, the UE may store the CHO information in a memory.

[0064] Therefore, instead of immediately performing a handover, the mobile terminal first maintains its connection to the source gNB and begins evaluating the CHO execution conditions for the target cell.

[0065] Finally, when the CHO execution conditions are met, the UE performs a handover to the target cell, which may include, for example, the UE detaching from the source gNB, applying stored configurations corresponding to the target cell, synchronizing to the target cell, and completing the handover (e.g., sending an RRCReconfigurationComplete message to the target gNB). The target cell may notify the source gNB that the UE has successfully accessed the target cell (see the CHO Execution Notification message in FIG. 9). One example is another XnAp message, such as the Handover Success signaling message of 3GPP TS 38.423.

[0066] There are several options for how to implement the condition for CHO. The condition shall define the criteria for when to apply the stored handover command, and the criteria shall be based for example on the quality of the serving and neighboring cells (somewhat similar to the conditions that lead the mobile terminal to send a measurement report when the condition is met). However, instead of triggering the transmission of a measurement report, the UE triggers CHO towards the target cell.

[0067] For example, the network can be configured to cause the wireless terminal to perform CHO when a neighboring cell has a better offset than the serving cell (e.g., similar to event A3), or when the serving cell is worse than a first threshold and the neighboring cell is between a second threshold (e.g., similar to event A5). Measurements for determining cell quality can be based on measurements such as quality represented by Radio Signal Received Power (RSRP), Radio Signal Received Quality (RSRQ), and Signal to Interference and Noise Ratio (SINR). Two (or more) (sub)conditions can also be configured for the mobile terminal, and a stored command can be associated with these multiple (sub)conditions. That is, the command is applied only if all (sub)conditions are met.

[0068] As a further example of CHO, if a CHO configuration is configured in a UE and another (legacy) HO command is received from a gNB before the CHO execution conditions are met, the UE performs handover based on the received (legacy) HO command and does not wait for any of the CHO conditions to be met. In short, legacy handover takes priority over CHO.

[0069] According to one example embodiment, the illustrated CHO configuration includes a configuration of CHO candidate cells (generated by the candidate gNB) and respective execution conditions (generated by the source gNB). For example, the CHO candidate cell configuration may include a candidate cell list with corresponding cell IDs and carrier frequencies of the candidate cells. The execution conditions may include CHO-related trigger events, such as the A3 / A5 events mentioned above, and trigger quantities (e.g., RSRP and RSRQ, RSRP and SINR, etc.).

[0070] An exemplary 5G compliant implementation of conditional handover is briefly described below, but more detailed information is available from 3GPP technical specifications including, for example, TS 38.331 v17.1.0, 38.300 v17.1.0, and 38.423 v17.1.0.

[0071] TS 38.331 defines the RRCReconfiguration procedures and messages used as part of CHO, as well as the corresponding UE behavior (e.g., sections 5.3.5, 5.3.5.1, 5.3.5.2, 5.3.5.3, and 5.3.5.4). Conditional reconfiguration is defined in clause 5.3.5.13 of TS 38.331 and is used by the network to configure one or more candidate SpCells for the UE. The network provides configuration parameters for the target SpCell in the ConditionalReconfiguration IE as part of the RRCReconfiguration IE. The ConditionalReconfiguration IE provides the configuration of candidate target SpCells and execution conditions for conditional handover, conditional PSCell addition (CPA, described below), and conditional PSCell modification (CPC, described below).

[0072] ConditionalReconfiguration The IE ConditionalReconfiguration is used to add, change, and remove conditional reconfiguration settings.

[0073] ConditionalReconfiguration information element -- ASN1START -- TAG-CONDITIONALRECONFIGURATION-START ConditionalReconfiguration-r16 ::= SEQUENCE { attemptCondReconfig-r16 ENUMERATED {true} OPTIONAL, -- Cond CHO condReconfigToRemoveList-r16 CondReconfigToRemoveList-r16 OPTIONAL, -- Need N condReconfigToAddModList-r16 CondReconfigToAddModList-r16 OPTIONAL, -- Need N ... } CondReconfigToRemoveList-r16 ::= SEQUENCE (SIZE (1.. maxNrofCondCells-r16)) OF CondReconfigId-r16 -- TAG-CONDITIONALRECONFIGURATION-STOP -- ASN1STOP [Table 1] [Table 2]

[0074] CondReconfigToAddModList The IE CondReconfigToAddModList relates to the list of conditional reconfigurations to add or modify, and for each entry contains a condReconfigId and the associated condExecutionCond / condExecutionCondSCG and condRRCReconfig.

[0075] CondReconfigToAddModList information element -- ASN1START -- TAG-CONDRECONFIGTOADDMODLIST-START CondReconfigToAddModList-r16 ::= SEQUENCE (SIZE (1.. maxNrofCondCells-r16)) OF CondReconfigToAddMod-r16 CondReconfigToAddMod-r16 ::= SEQUENCE { condReconfigId-r16 CondReconfigId-r16, condExecutionCond-r16 SEQUENCE (SIZE (1..2)) OF MeasId OPTIONAL, -- Need M condRRCReconfig-r16 OCTET STRING (CONTAINING RRCReconfiguration) OPTIONAL, -- Cond condReconfigAdd ..., [[ condExecutionCondSCG-r17 OCTET STRING (CONTAINING CondReconfigExecCondSCG-r17) OPTIONAL -- Need M ]] } CondReconfigExecCondSCG-r17 ::= SEQUENCE (SIZE (1..2)) OF MeasId -- TAG-CONDRECONFIGTOADDMODLIST-STOP -- ASN1STOP [Table 3] [Table 4]

[0076] CondReconfigId The IE CondReconfigId is used to identify the configuration of the CHO, CPA, or CPC.

[0077] CondReconfigId Information Element -- ASN1START -- TAG-CONDRECONFIGID-START CondReconfigId-r16 ::= INTEGER (1.. maxNrofCondCells-r16) -- TAG-CONDRECONFIGID-STOP -- ASN1STOP Additionally, TS 38.331 defines the ReportConfigNR IE in section 6.3.2, which specifies the criteria for triggering a CHO, CPA, or CPC event.

[0078] TS 38.300 defines conditional handover in subclause 9.2.3.4 as a handover performed by a UE when one or more handover execution conditions are met. The UE starts evaluating the execution conditions when it receives the CHO configuration and stops evaluating the execution conditions when the handover is performed. Furthermore, the execution conditions can consist of one or two trigger conditions. Only a single RS type is supported, and up to two different trigger quantities (e.g., RSRP and RSRQ, RSRP and SINR, etc.) can be simultaneously configured for the evaluation of the CHO execution conditions for a single candidate cell. Subclause 16.4.3.2.2 describes CHO as applied to non-terrestrial networks.

[0079] As an example of a general conditional handover, multiple candidate target cells can be pre-provisioned within the network, rather than having only one target cell as in the legacy case. This can be beneficial because handover delays can lead to uncertainty about the specific target cell that the mobile terminal will access. In response, the mobile terminal receives various target cell configurations and CHO trigger conditions for each monitored target cell configuration. When the conditions for one of the configured candidate target cells are met, the mobile terminal performs a handover to that target node based on the target cell configuration already received.

[0080] CHO in a scenario with multiple candidate target cells (here, two candidate target cells, gNB1 and gNB2) is shown in Figure 10. Figure 10 is a signaling diagram similar to that shown in Figure 9, which illustrates a scenario with one candidate target cell. The signaling diagram is mostly similar to Figure 9, except that CHO preparation is performed for the two candidate target cells and is controlled by gNB1 and gNB2, respectively. As is clear from Figure 10, CHO preparation, including CHO request and CHO ACK, is shown in a simplified manner as double-sided arrows for the two candidate target cells, gNB1 and gNB2.

[0081] The source gNB determines the CHO execution conditions for each candidate target cell and provides the mobile terminal with the CHO configurations for both candidate target cells and each CHO execution condition.

[0082] Furthermore, it is exemplarily assumed that the source gNB transmits to the UE the CHO configurations of the two candidate target cells together with the respective CHO execution conditions for each CHO configuration, or these may be transmitted separately to the UE for each candidate target cell.

[0083] In the scenario of Figure 10, it is exemplarily assumed that the mobile terminal determines that the CHO execution conditions for the target gNB2 are met and therefore performs a handover to the target cell of gNB2.

[0084] The conditional handover procedure in Figure 10 further includes two important steps. First, after the CHO is successfully completed, the UE releases (e.g., deletes from storage) all CHO configurations and CHO execution conditions, including those of gNB1's candidate target cells for which CHO was not triggered. Second, upon receiving a CHO execution notification message from target cell gNB2, the source gNB notifies gNB1 that the CHO of the mobile terminal has been canceled. This allows gNB1 to release any resources that may have been reserved for a potential CHO of the mobile terminal.

[0085] <Conditional PSCell change> 3GPP Release 16 also introduces the Conditional PSCell change procedure (CPC) to improve mobility robustness of PSCell changes in dual connectivity scenarios.

[0086] In DC (dual connectivity, e.g., MR-DC), a PSCell change procedure can be performed to change the PSCell of the secondary cell group. In one example, the PSCell may depend on whether a security key change is required.

[0087] Similar to CHO, a conditional PSCell change (CPC) is executed only if the corresponding CPC execution condition is met.

[0088] CPC reuses many of the features of the conditional handover described above (see 10.1 of TS 37.340 v17.1.0).

[0089] The UE completes the CPC execution procedure with an RRCReconfigurationComplete message to the Master Node (MN) (of the MCG). If SRB3 is not configured, it contains an embedded RRCReconfigurationComplete message for the new PSCell, otherwise the UE sends the RRCReconfigurationComplete directly to the new PSCell.

[0090] A 5G compliant implementation is specified in TS 37.340 v17.1.0, which provides details of CPC in section 10.6 as follows:

[0091] The CPC configuration includes the configuration and execution conditions of the CPC candidate PSCell, and may include the MCG configuration for inter-SN CPC that is applied when CPC execution is triggered.

[0092] An execution condition may consist of, for example, one or two trigger conditions (CondEvents, defined in TS 38.331 or TS 36.331). Only a single RS (Reference Signal) type and up to two different trigger quantities (e.g., RSRP and RSRQ, RSRP and SINR, etc.) may be used to evaluate the CPC execution condition of a single candidate PSCell.

[0093] If a PSCell change command or PCell change command is issued before any of the CPC execution conditions are met, the UE will perform the PSCell change procedure described in clauses 10.3 and 10.5 of TS 38.300 or the PCell change procedure described in clause 9.2.3.2 of TS 38.300 or clause 10.1.2.1 of TS 36.300, regardless of the previously received CPC setting.

[0094] While executing the CPC, the UE does not need to continue evaluating the execution conditions of other candidate PSCells.

[0095] If the CPC procedure is successfully performed, the UE shall release all stored conditional reconfigurations (eg, conditional reconfigurations for CPC and CHO as specified in TS 38.300 or TS 36.300).

[0096] When the SCG is released, the UE releases the stored CPC settings.

[0097] In Release 16, the CPC procedure was limited to intra-SN changes without MN involvement. 3GPP Release 17 introduced support for inter-SN Conditional PSCell Change (CPC).

[0098] FIG. 11 shows an exemplary simplified signaling diagram of the CPC procedure. As can be seen from FIG. 11, the source gNB prepares CPC with both candidate target cells, gNB1 and gNB2. Preparation may include, for example, the source gNB receiving CPC configuration parameters for each of gNB1 and gNB2 and determining CPC execution conditions for each of the two CPC candidates. The two CPC configurations (including the CPC configuration parameters and each CPC execution condition) are then transmitted from the source gNB to the UE. The UE evaluates the CPC execution conditions for the two candidates rather than immediately changing the PSCell to one of the two candidate target cells. Finally, the UE determines that the CPC execution condition for target gNB2 is met and changes the PSCell to gNB2's cell. Upon successful completion of CPC, the UE releases the two CPC configurations, including the CPC configuration for gNB1 on which CPC was not performed.

[0099] <Conditional PSCell addition> 3GPP also introduces the Conditional PSCell Addition (CPA) procedure to improve mobility robustness when creating a new secondary cell group. According to CPA, a PSCell is added for a secondary cell group in a dual connectivity scenario, and the UE connects to a new PSCell in the SCG in addition to the cells in the MCG. In one example, the additional PSCell can be a PSCell of a different radio access technology than the current PSCell. CPA can also be used to add another SCell to an SCG. Furthermore, under dual connectivity, multiple SCGs can be established for a UE, but only one SCG can be active at a time. Therefore, CPA can also be used to create another SCG that is initially inactive but has another PSCell.

[0100] Similar to CHO, Conditional PSCell Addition (CPA) is defined as a PSCell addition that is performed by the UE only if the corresponding CPA execution condition is met. When the UE receives a CPA configuration, it starts evaluating the execution condition, and when a PSCell addition or PCell change is triggered, it stops evaluating the execution condition.

[0101] CPA reuses many of the features of the conditional handover described above (see TS 37.340 v17.1.0, section 10.1).

[0102] In one embodiment, the CPA procedure is used to establish a connection between the UE and an additional PSCell of the newly created SCG, including the configuration parameters of the PSCell.

[0103] Section 10.2.3 of TS 37.340 v17.1.0 discloses conditional PSCell addition as part of the secondary node addition in Section 10.2. According to this 5G-compliant embodiment, the CPA configuration includes the configuration of the CPA candidate PSCell, the execution conditions, and may include the MCG configuration to be applied when CPA execution is triggered. The execution conditions may consist of one or two trigger conditions (CondEvents, defined in TS 38.331 [4] or TS 36.331

[10] ). Only a single RS type and up to two different trigger quantities (e.g., RSRP and RSRQ, RSRP and SINR, etc.) can be used to evaluate the CPA execution conditions for a single candidate PSCell.

[0104] If the UE receives a normal (i.e., non-conditional) PSCell addition or PCell modification command before any of the CPA execution conditions are met, the UE shall perform the PSCell addition procedure described in clause 10.2.1 or clause 10.2.2 of TS 38.300 or the PCell modification procedure described in clause 9.2.3.2 of TS 38.300 or clause 10.1.2.1 of TS 36.300, regardless of the previously received CPA configuration. Upon successful completion of the PSCell addition or PCell modification procedure, the UE shall release the stored CPA configuration.

[0105] While performing CPA, the UE does not need to continue evaluating the execution conditions of other candidate PSCells.

[0106] If the CPA procedure is successfully performed, the UE releases all stored conditional reconfigurations (i.e., conditional reconfigurations for CPA and CHO as specified in TS 38.300 or TS 36.300). It does not support CPA configuration in HO commands, PSCell addition commands, or conditional configurations (i.e., configuration of CPA, CPC, or CHO).

[0107] An exemplary and simplified signaling diagram of the CPA procedure is shown in Figure 12. As can be seen from the diagram, the source gNB (which can therefore be considered a cell of the master cell group) prepares CPA with both candidate target cells, gNB1 and gNB2. Preparation may include, for example, the source gNB receiving CPA configuration parameters for gNB1 and gNB2, respectively, and the source gNB determining CPA execution conditions for each of the two CPA candidates. The two CPA configurations (including the CPA configuration parameters and respective CPA execution conditions) are then transmitted from the source gNB to the UE. The UE evaluates the CPA execution conditions for the two candidates rather than immediately adding the PSCell for gNB1 or gNB2. Finally, the UE determines that the CPA execution conditions for target gNB2 are satisfied and creates an SCG with the PSCell for gNB2. Upon successful completion of CPA, the UE releases the two CPA configurations, including the CPA configuration for gNB1, on which CPA was not performed.

[0108] <Further improvements> Above we have described the mobility extensions for CHO, CPC, and CPA introduced by 3GPP Releases 16 and 17. Further extensions to NR mobility are envisioned in Release 18.

[0109] The inventors identified problems with the current definitions of the CHO, CPC, and CPA procedures. In particular, the current Release 16 and 17 NR specifications require the UE to deconfigure CHO / CPC / CPA, respectively, upon successful completion of the corresponding procedures.

[0110] For example, as shown in FIG. 10, once the CHO is successfully completed, the UE releases all CHO configurations, including the CHO configuration parameters and CHO execution conditions.

[0111] As shown in FIG. 11, when the CPC is successfully completed, the UE releases all CPC configurations, including the CPC configuration parameters and CPC execution conditions.

[0112] As shown in FIG. 12, when the CPA is successfully completed, the UE releases all CPA configurations, including the CPA configuration parameters and CPA execution conditions.

[0113] As a result, the network and the UE need to reconfigure and reinitialize the CHO / CPC / CPA so that another subsequent CHO / CPC / CPA can be performed, as described above in relation to Figures 10, 11 and 12, respectively.

[0114] This increases the signaling overhead: after each successful CHO / CPC / CPA procedure, the UE needs to receive again the complete set of configuration parameters and execution conditions for each candidate cell.

[0115] Furthermore, this may lead to increased delays in the CHO / CPC / CPA procedure, as the UE must first be configured after successfully completing CHO / CPC / CPA before being able to run CHO / CPC / CPA again.

[0116] The above drawbacks are particularly noticeable in cases where there are frequent cell changes, for example, when operating in FR2 (which includes the frequency band from 24.25 GHz to 71.0 GHz).

[0117] The inventors have thus found it possible to provide improved mobility procedures (CHO, CPC, CPA, etc.) that make it possible to avoid one or more of the above-mentioned disadvantages. The present invention relates to various solutions and variants of such improved mobility procedures.

[0118] <Embodiment> In the following, UEs, base stations, and procedures for meeting these needs are described for new radio access technologies envisioned for 5G mobile communication systems, but may also be used in previous LTE mobile communication systems or future mobile communication systems. Various implementations and variations are also described. The following disclosure is facilitated by, and may be based, for example, at least in part on, the above discussion and findings.

[0119] In general, it should be noted that many assumptions have been made herein and will be made hereinafter in order to be able to explain the principles underlying the present disclosure in a clear, concise, and understandable manner. However, these assumptions should be understood as merely examples made herein for the purpose of explanation, and they are not necessarily essential to the present invention, and therefore should not limit the scope of the present disclosure. Those skilled in the art will recognize that the principles of the following disclosure and claims can be applied in different scenarios and in ways not explicitly described herein.

[0120] Furthermore, although some of the terms used below, such as procedures, entities, and layers, are closely related to those used in the LTE / LTE-A system or the current 3GPP 5G standardization, specific terms used in the context of new radio access technologies for upcoming communication systems have not yet been fully determined or may eventually change. Thus, terms may change in the future without affecting the functionality of the embodiments. As a result, those skilled in the art will recognize that the embodiments and their scope of protection should not be limited to the specific terms used exemplified in this specification, which lack newer or final agreed-upon terms, but should be more broadly understood by the functions and concepts underlying the solutions described in this disclosure.

[0121] For example, a mobile station or mobile node or user terminal or user equipment (UE) is a physical entity (physical node) in a communication network. A node may have several functional entities. A functional entity refers to a software or hardware module that implements and / or provides a predetermined set of functions to other functional entities of the same or another node or network. A node may have one or more interfaces that attach the node to a communication facility or medium that allows the node to communicate. Similarly, a network entity may have logical interfaces that attach a functional entity to a communication facility or medium that allows the node to communicate with other functional entities or corresponding nodes.

[0122] The term "base station" or "radio base station" in this specification refers to a physical entity in a communication network. Similar to a mobile station, a base station may have several functional entities. A functional entity refers to a software or hardware module that implements and / or provides a predetermined set of functions to other functional entities of the same or another node or network. A physical entity performs several control tasks for communication devices, including one or more of scheduling and configuration. Note that base station functionality and communication device functionality may be integrated within a single device. For example, a mobile terminal may also implement base station functionality for other terminals. While the term used in LTE is eNB (or eNodeB), the term currently used for 5G NR is gNB. A base station may also be a gNB in a Non-Terrestrial Network (NTN) NR system.

[0123] Communication between a UE and a base station is typically standardized and may be defined by different layers, such as PHY, MAC, RRC, etc. (see background discussion above).

[0124] The expression "initial cell configuration" here can be understood as a configuration of a cell that can be used in the context of performing a cell mobility procedure, such as a CHO, CPC, or CPA procedure. The term "initial" in such a context refers to the cell configuration being exchanged for the first time (e.g., between communication parties) and may therefore be complete in the sense that it contains the complete parameter set of the cell. As an example, the initial cell configuration may further include "execution conditions," limiting the execution of the cell mobility procedure to the fulfillment of the conditions.

[0125] The "initial cell configuration" can be distinguished from the "differential cell configuration" that is used after the "initial cell configuration" (after successfully executing a cell mobility procedure). The "differential" in such a connection refers to the fact that the "differential cell configuration" is about differences with respect to the initial cell configuration, and therefore may be (but is not necessarily) likely to be reduced compared to the complete "initial cell configuration."

[0126] Furthermore, the expression "updated cell configuration" can be understood as different from both the initial cell configuration and the differential cell configuration. As an example, the updated cell configuration may be obtained based on the initial cell configuration and the differential cell configuration, where the initial cell configuration is modified according to the differential cell configuration, for example, by replacing, adding, or deleting elements of the cell configuration.

[0127] The expression "cell configuration parameters" refers to parameters related to a cell (more precisely, a candidate target cell), which can be used to perform a conditional cell mobility procedure in that cell.

[0128] The expression "candidate target cell" may be understood to refer to a cell that is a candidate for being subject to a conditional cell mobility procedure. There may be one or more candidate target cells, one of which is likely to be the actual target cell of the conditional cell mobility procedure.

[0129] The expression "conditional cell mobility procedure" can be understood to include mobility procedures relating to different cells, the execution of which is not immediate but depends on the fulfillment of execution conditions. Examples of conditional cell mobility procedures include conditional handover (CHO, see e.g., CHO in the 5G standard described above), conditional cell change (CPC, see e.g., CPC in the 5G standard described above), or conditional cell addition (CPA, see e.g., CPA in the 5G standard described above).

[0130] The term "cancel" can be understood, for example, in relation to the cancellation of a setting, for example, to "delete" a (stored) setting.

[0131] The term "maintain" can mean, for example, in relation to maintaining a setting, for example, being set not to be released, for example, not releasing the setting.

[0132] 13 shows a general, simplified, exemplary block diagram of a user equipment (also referred to as a communication device) and a scheduling device (here assumed for illustrative purposes to be located in a base station such as an LTE eNB (also known as an ng-eNB) or a gNB in 5G NR). The UE and the eNB / gNB communicate with each other over a (wireless) physical channel using their respective transceivers.

[0133] A communication device may include a transceiver and a processing circuit. The transceiver may include a receiver and a transmitter and / or function as both a receiver and a transmitter. The processing circuit may be one or more hardware components, such as one or more processors or any LSI. An input / output point (or node) exists between the transceiver and the processing circuit, and the processing circuit can control the transceiver during operation through the input / output point, i.e., control the receiver and / or transmitter to exchange receive / transmit data. The transceiver may include an RF (radio frequency) front end, including one or more antennas, amplifiers, and RF modulators / demodulators, as a transmitter and receiver. The processing circuit may perform control tasks, such as controlling the transceiver to transmit user data and control data provided by the processing circuit and / or receiving user data and control data that are further processed by the processing circuit. In addition, the processing circuit may be responsible for performing other processes, such as judgment, determination, calculation, and measurement. The transmitter may be responsible for performing the transmission process and other processes related thereto. The receiver may be responsible for performing the process of reception and other processes related thereto, such as monitoring the channel.

[0134] Various solutions for improved mobility procedures are described below. In this connection, an improved UE, an improved base station, and an improved integrated circuit are presented, which participate separately or together in the improved mobility procedures. Corresponding methods for the UE behavior and the base station behavior are also provided. The integrated circuit corresponds to the UE and the base station and their respective behaviors.

[0135] The improved mobility procedures are given below.

[0136] Figure 14 illustrates a simplified exemplary UE structure for one exemplary implementation of improved mobility procedures, which may be implemented based on the general UE structure described in connection with Figure 13. The various structural elements of the UE illustrated in Figure 14 may be interconnected with each other, e.g., by corresponding input / output nodes (not shown), for example, to exchange control and user data and other signals. Although not shown for purposes of illustration, the UE may include additional structural elements.

[0137] As can be seen from FIG. 14, the UE may include an initial cell configuration receiving unit (for receiving an initial cell configuration including cell configuration parameters and execution conditions), an execution condition evaluation circuit, a conditional cell mobility procedure circuit, and an initial cell configuration maintenance circuit.

[0138] In this case, the receiver of the UE may be exemplarily configured to at least partially perform one or more of receiving an initial cell configuration for at least one candidate target cell, and further, as will become apparent from the disclosure below, receiving a differential cell configuration, etc.

[0139] As will become apparent from the disclosure below, in this case, the processing circuitry of the UE may be exemplarily configured to at least partially perform one or more of: executing a conditional cell mobility procedure if an execution condition is met; maintaining the received initial cell configuration; generating an updated cell configuration based on the initial cell configuration and the differential cell configuration; etc.

[0140] As will become apparent from the disclosure below, in this case, the transmitter of the UE may be illustratively configured to at least partially perform one or more of the following: send measurement reports to the UE's serving cell.

[0141] One exemplary procedure, disclosed in further more detail below, is implemented by a UE including: a receiving unit that receives, from a source base station, an initial cell configuration of at least one candidate target cell, each initial cell configuration including cell configuration parameters for each candidate target cell for performing a conditional cell mobility procedure and an execution condition regarding when to perform the conditional cell mobility procedure at each candidate target cell; a circuit in the UE that, when the execution condition for one of the at least one candidate target cell is satisfied, performs the conditional cell mobility procedure at the target cell based on the cell configuration parameters of the target cell; and, when the conditional cell mobility procedure between the UE and the target cell is successfully completed, maintains the received initial cell configuration of the at least one candidate target cell.

[0142] A corresponding exemplary method includes the following steps performed by the UE.

[0143] receiving, from the source base station, an initial cell configuration of at least one candidate target cell, where each initial cell configuration includes cell configuration parameters for each candidate target cell for performing a conditional cell mobility procedure between the UE and each candidate target cell, and an execution condition for when to perform the conditional cell mobility procedure in each candidate target cell; performing a conditional cell mobility procedure in the target cell of at least one candidate target cell based on cell configuration parameters of the target cell when an execution condition for the target cell is satisfied; Upon successful completion of the conditional cell mobility procedure between the UE and the target cell, maintaining the received initial cell configuration of at least one candidate target cell. A sequence diagram corresponding to exemplary UE behavior along the UE and UE methods discussed above is shown in FIG.

[0144] Thus, the improved mobility procedure achieves the objectives and overcomes some of the drawbacks mentioned above. For example, the improved mobility procedure maintains the initial cell configuration upon successful completion of the conditional cell mobility procedure, rather than releasing the initial cell configuration as in prior art solutions. This allows the cell configuration to be reconfigured or updated based on the maintained initial cell configuration, thereby saving over-the-air signaling overhead between the UE and the base station. As a further advantage, the improved mobility procedure can speed up subsequent conditional cell mobility procedures, since the maintained initial cell configuration is still accessible and reusable by the UE.

[0145] Some exemplary embodiments of the improved mobility procedure include improved base stations, particularly an improved source base station to which the UE is currently connected (e.g., referred to as a serving base station because it serves the UE), and an improved target base station that is the subject of the conditional cell mobility procedure. Accordingly, the improved mobility procedure also provides for improved base stations that participate in the mobility procedure, as described below.

[0146] Figure 16 illustrates a simplified exemplary source base station structure according to one exemplary implementation of the improved mobility procedures, which may be implemented based on the general base station structure described in connection with Figure 13. The various structural elements of the source base station illustrated in Figure 16 may be interconnected with each other, e.g., by corresponding input / output nodes (not shown), e.g., for exchanging control and user data and other signals. Although not shown for purposes of illustration, the source base station may include additional structural elements.

[0147] As is clear from this, the source base station comprises an initial cell setting transmitter (the initial cell setting includes cell setting parameters and execution conditions), a success notification receiver, a circuit for generating differential cell setting parameters, and a transmitter for transmitting the differential cell setting parameters.

[0148] As will become apparent from the disclosure below, in this case, the receiving unit of the source base station may be configured to at least partially perform one or more of, for example, receiving a success notification, receiving requested cell configuration parameters, etc.

[0149] As will become apparent from the disclosure below, in this case, the processing circuitry of the source base station may be configured to at least partially perform one or more of, for example, determining differential cell configuration parameters for each candidate target cell.

[0150] As will become apparent from the disclosure below, in this case, the transmitter of the source base station may be configured to at least partially perform one or more of, for example, sending an initial cell configuration to the UE, sending a request to a candidate target cell requesting cell configuration parameters, sending differential cell configuration parameters to the target base station, etc.

[0151] As disclosed in more detail below, an example procedure is performed by a source base station, including: a transmitter unit transmitting initial cell configurations of at least one candidate target cell to a user equipment (UE), each initial cell configuration including cell configuration parameters of each candidate target cell for performing a conditional cell mobility procedure and an execution condition regarding timing for performing the conditional cell mobility procedure between the UE and each candidate target cell; a receiver unit receiving, from a target base station of a target cell among the at least one candidate target cell, a notification regarding successful completion of the conditional cell mobility procedure between the UE and the target cell; after receiving the notification regarding successful completion of the conditional cell mobility procedure, the transmitting unit transmits, to one or more candidate target cells among the candidate target cells for which the conditional cell mobility procedure has not been performed, a request to request cell configuration parameters of each candidate target cell for performing the conditional cell mobility procedure between the UE and each candidate target cell; a receiving unit receiving requested cell configuration parameters from one or more candidate target cells in response to the transmitted request; the base station circuitry determines differential cell configuration parameters for each of the one or more candidate target cells for which the requested and received cell configuration parameters were received, the differential cell configuration parameters including cell configuration parameters that differ from the cell configuration parameters of the initial cell configuration of each candidate target cell; The sending unit sends differential cell configuration parameters of one or more candidate target cells to a target base station of the target cell. A corresponding method includes the following steps, which are performed by a source base station:

[0152] sending to a user equipment (UE) an initial cell configuration of at least one candidate target cell, each initial cell configuration comprising cell configuration parameters for each candidate target cell for performing a conditional cell mobility procedure between the UE and each candidate target cell and an execution condition for when to perform the conditional cell mobility procedure between the UE and each candidate target cell; receiving a notification from a target base station of a target cell among the at least one candidate target cell regarding successful completion of a conditional cell mobility procedure between the UE and the target cell; After receiving notification about the successful completion of the conditional cell mobility procedure, sending a request to one or more candidate target cells among the candidate target cells for which a conditional cell mobility procedure has not been performed, requesting cell configuration parameters of each candidate target cell for performing a conditional cell mobility procedure between the UE and each candidate target cell; receiving requested cell configuration parameters from one or more candidate target cells in response to the transmitted request; determining differential cell configuration parameters for each of the one or more candidate target cells for which the requested and received cell configuration parameters were received, the differential cell configuration parameters including cell configuration parameters that differ from cell configuration parameters of the initial cell configuration of each candidate target cell; Sending differential cell configuration parameters of one or more candidate target cells to a target base station of the target cell.

[0153] A sequence diagram corresponding to an exemplary source base station operation in accordance with the source base station and corresponding method discussed above is shown in Figure 17. This sequence diagram illustrates an exemplary simplified implementation of the source base station method presented above.

[0154] Figure 18 shows a simplified exemplary target base station structure for an exemplary implementation of the improved mobility procedure, which can be implemented based on the general base station structure described in relation to Figure 13. The various structural elements of the target base station shown in Figure 18 can be connected to each other, for example, by corresponding input / output nodes (not shown) for exchanging control and user data and other signals. Although not shown, the target base station may include additional structural elements.

[0155] As is clear from the figure, the target base station includes an initial cell setting parameter transmission unit, a conditional cell mobility procedure circuit, a circuit for acquiring differential cell setting parameters, a determination circuit for determining execution conditions, and a differential cell setting transmission unit.

[0156] As will become apparent from the disclosure below, in this case the receiver of the target base station may be configured to at least partially perform one or more of, for example, receiving reception cell configuration parameters.

[0157] As will become apparent from the disclosure below, in this case the processing circuitry of the target base station may be configured to at least partially perform, for example, one or more of: performing a conditional cell mobility procedure, obtaining different cell configuration parameters, determining execution conditions, etc.

[0158] As will become apparent from the disclosure below, in this case, the transmitter of the target base station may be configured to at least partially perform one or more of, for example, transmitting initial cell configuration parameters, transmitting differential cell configurations, etc.

[0159] As disclosed in more detail below, an example procedure is performed by a target base station, including: a transmitter of the target base station transmits, to a source base station, initial cell configuration parameters for performing a conditional cell mobility procedure between a user equipment (UE) and a base station serving the target cell; circuitry of the target base station performs, based on the transmitted initial cell configuration parameters, the conditional cell mobility procedure with the UE, thereby connecting the UE to the target cell.

[0160] The circuitry of the target base station obtains differential cell configuration parameters for one or more candidate target cells for performing a conditional cell mobility procedure between the UE and each of the one or more candidate target cells. The differential cell configuration parameters for the candidate target cells include parameters that are different from initial cell configuration parameters for performing the conditional cell mobility procedure between the UE and each of the candidate target cells. The circuitry determines, for each of the one or more candidate target cells, an execution condition for when to perform the conditional cell mobility procedure between the UE and each of the candidate target cells.

[0161] The transmitter transmits to the UE a differential cell configuration for each of the one or more candidate target cells, the differential cell configuration including the determined differential cell configuration parameters and the determined execution conditions for the one or more candidate target cells.

[0162] The corresponding method includes the following steps, which are performed by the target base station: sending, to a source base station, initial cell configuration parameters for performing a conditional cell mobility procedure between a user equipment (UE) and a base station serving the target cell; performing a conditional cell mobility procedure with the UE based on the transmitted initial cell configuration parameters, thereby causing the UE to connect to the target cell; obtaining differential cell configuration parameters of one or more candidate target cells for performing a conditional cell mobility procedure between the UE and each of the one or more candidate target cells, wherein the differential cell configuration parameters of the candidate target cells include parameters that are different from initial cell configuration parameters for performing the conditional cell mobility procedure between the UE and each of the candidate target cells; determining, for each of the one or more candidate target cells, an execution condition regarding when to perform a conditional cell mobility procedure between the UE and each candidate target cell; sending to the UE a differential cell configuration for each of the one or more candidate target cells, the differential cell configuration including the determined differential cell configuration parameters for the one or more candidate target cells and the determined execution conditions.

[0163] A corresponding sequence diagram for an exemplary target base station behavior in accordance with the target base station and corresponding method described above is shown in Figure 19. The sequence diagram illustrates an exemplary simplified implementation of the target base station method described above.

[0164] As described above, the improved UE, improved source base station, and improved target base station achieve the objectives, overcome some of the identified problems, and achieve advantages by participating in improved mobility procedures.

[0165] Improved mobility procedures involving improved devices are described below.

[0166] For purposes of explanation and illustration, we first exemplarily assume that the improved mobility procedure is an improved conditional handover procedure (improved CHO procedure). In general, conditional handover can be understood as a procedure in which, upon satisfying a condition, a UE disconnects from a source cell and connects to one candidate target cell (potentially selected from among many candidates). Conditional handover can be used regardless of whether the UE is in dual connectivity. Thus, CHO can be used to change the UE's primary cell, and in dual connectivity, to change the UE's primary cell when the primary cell is part of the UE's master cell group.

[0167] However, this assumption of CHO as an improved conditional cell mobility procedure should not be understood to mean that the improved mobility procedure should be limited only to conditional handover. Rather, the principles underlying the improved mobility procedure are also applicable to other conditional cell mobility procedures, such as the conditional cell change procedure (e.g., see CPC above) and the conditional cell addition procedure (e.g., see CPA above). A more detailed description of the improved CPC and improved CPA procedures is provided below.

[0168] Figure 20 is a signaling diagram of an exemplary simplified implementation of the improved CHO procedure, showing the exchange of messages between the different participating entities (here UE, gNB0, gNB1, and gNB2) and the steps performed by these entities.

[0169] The improved CHO procedure can be the same as (or similar to) the regular CHO procedure, for example, as described above in connection with Figures 8, 9, or 10, until the CHO is successfully completed.

[0170] Important steps and messages for the improved CHO procedure relate to the point after successful completion of CHO, including the UE maintaining the initial CHO configuration, at least for the candidate gNB2 (which is the configuration for a CHO that was prepared but not executed). Thus, the initial CHO configuration is not deleted from the UE memory at this point. This is in contrast to legacy CHO procedures (e.g., the procedures described in Figures 8, 9, or 10), in which the UE clears all initial CHO configuration upon successful CHO.

[0171] Furthermore, the UE's new serving cell gNB1 then acquires a differential CHO configuration (here, only that of gNB2) and provides the differential CHO configuration to the UE. The process of acquiring a differential CHO configuration will be described later in various embodiments. In general, the differential CHO configuration may reflect differences between the new (updated) CHO configuration of gNB2 (after the previous CHO configuration) and the initial CHO configuration of gNB2. The differential CHO configuration of the candidate target cell may include CHO configuration parameters and / or execution conditions that differ from the initial CHO configuration of the candidate target cell. The differences may be, for example, updated parameters (e.g., changed values), parameters that may be new parameters, or released parameters (i.e., parameters that are not present in the CHO configuration).

[0172] Thus, in one example, the differential CHO configuration may be smaller in size because it does not include some or all elements that have not changed.

[0173] Exemplary parameters that can be changed after CHO are, for example, a different candidate cell list (in the new gNB), a different cell ID of the new gNB, a different carrier frequency, etc. However, the execution conditions can also be changed, for example, different sub-conditions can be defined, different measurement quantities or different measurement thresholds can be defined.

[0174] The UE receives a differential CHO configuration for one candidate target gNB2 from gNB1. The UE generates an updated CHO configuration for gNB2 based on the received differential CHO configuration and the stored initial CHO configuration. In this way, the updated CHO configuration is complete and up-to-date for use for potential CHO for gNB2 in the future.

[0175] According to another example (not shown), when CHO to gNB1 is successfully completed, the UE may cancel the initial CHO configuration of gNB1 because the initial CHO configuration of gNB1 is no longer necessary considering that the UE has already been successfully connected to gNB1. However, the CHO configuration of other candidate target cells (gNB2 in FIG. 20) is maintained by the UE.

[0176] The above improved CHO procedure assumed that only two different candidate target cells gNB1 and gNB2 had initial CHO configurations prepared. Accordingly, once either CHO is completed, only one differential CHO configuration needs to be prepared and provided to the UE. However, the improved CHO procedure also applies a similar principle to the case where there are two or more candidate target cells. In this case, an initial CHO configuration is prepared for each candidate target cell and provided to the UE. Then, differential CHO configurations are prepared for some or all candidate target cells (excluding the UE's new serving cell after successful CHO) and provided to the UE.

[0177] It is also possible that after successful CHO, one or more of the candidate target cells do not accept the UE (e.g., due to lack of resources or inability of the UE to move from the new serving cell), thereby rejecting the new CHO preparation. In this case, no differential CHO configuration is prepared for the rejected target cells. In response, the UE does not receive differential CHO configuration for the rejected target cells, and may determine to release the initial cell configuration for the candidate target cells for which it has not received the differential cell configuration.

[0178] Another exemplary variant is applicable when there are two or more different candidate target cells for which differential CHO configurations are to be prepared. Illustratively, it is assumed that the candidate cells 1) can belong to only one cell group, 2) can belong to multiple cell groups (e.g., an MCG and other SCGs, or subgroups (e.g., within an MCG or SCG), or 3) the same cell can be configured as a PSCell in multiple cell groups. It is further assumed that the configurations of cells in the same cell group are identical. In other words, two candidate target cells in the same cell group can have the same configuration, e.g., the same CHO configuration. Therefore, according to this exemplary variant of the improved CHO procedure, it is sufficient to transmit only one differential CHO configuration for two different candidate target cells if these two candidate target cells belong to the same cell group that shares a common configuration. This has the advantage that less signaling needs to be transmitted when preparing a conditional handover.

[0179] Furthermore, although the above exemplary variants are described with respect to an improved conditional handover procedure and transmission of differential CHO configurations, the concept of two candidate cells sharing a common configuration can also be applied to improve the regular CHO procedure, especially for two different candidate target cells, only one initial (complete) CHO configuration needs to be transmitted if these two candidate target cells belong to the same cell group that shares a common configuration.

[0180] According to a further exemplary variation of the improved CHO procedure, functionality is provided in the UE to distinguish between legacy CHO behavior (including de-configuring the CHO upon successful completion of the CHO) and improved CHO behavior (including maintaining the CHO configuration as described above).

[0181] According to one example, the UE stores preconfiguration information indicating whether to follow legacy or improved CHO behavior. For example, the preconfiguration information is received from the source base station as part of RRC signaling. A new information element (IE) CondConfigRetain can be defined, for example, as part of the already existing IE ConditionalReconfiguration. The UE receives the new information element when receiving an RRCReconfiguration message from the source gNB during CHO.

[0182] According to another example, the UE may also obtain appropriate information from the candidate target cell, for example in the broadcast of system information, when connecting to the candidate target cell, for example via RACH.

[0183] Although not shown in Figure 20 (and Figures 21, 22, and 23 described later), according to another example implementation of the improved CHO procedure, the new serving cell gNB1 may obtain not only differential CHO configurations for the candidate target cells of gNB2, but also normal initial CHO configurations for the candidate target cells of gNB0 (i.e., the UE's previous serving cell). However, the UE cannot create a differential CHO configuration for gNB0 because it has not yet received the initial CHO configuration for gNB0. Instead, the UE's new serving cell gNB1 requests the necessary CHO configuration parameters from gNB0, determines appropriate execution conditions for performing the improved CHO between the UE and gNB0, and sends the corresponding initial CHO configuration for gNB0 to the UE.

[0184] One important aspect of the improved CHO procedure shown in Figure 20 relates to how the UE's new serving cell gNB1 acquires the differential CHO configurations for the other candidate target cells gNB2. There are various embodiments of the improved CHO procedure for how the UE's new serving cell gNB1 acquires the differential CHO configurations for the other candidate target cells gNB2. Three different exemplary embodiments are described below. Briefly, according to a first embodiment, the source gNB primarily determines the differential CHO configurations for all candidate target cells (see Figure 21). According to a second embodiment, each candidate target cell determines its own differential CHO configuration (see Figure 22). According to a third embodiment, the new serving cell primarily determines the differential CHO configurations for all candidate target cells (see Figure 23).

[0185] For purposes of describing the three examples shown in Figures 21, 22, and 23, it is exemplarily assumed that a conditional handover has been prepared for a UE at candidate target cells gNB1 and gNB2. Also, the upper portions of Figures 21, 22, and 23 described below illustrate the conditional handover in an abbreviated form, with only the final steps, particularly those related to performing a CHO to candidate gNB2, shown within the dashed box labeled "Successful Conditional Handover Procedure." It should be noted that the dashed boxes in Figures 21, 22, and 23 correspond, for example, to the dashed boxes described in connection with Figure 10, and thus may include previous steps performed for a successful conditional handover procedure, particularly the above-described preparation of a conditional handover with candidate target cells gNB1 and gNB2.

[0186] From the UE's perspective, the three different embodiments are identical, since in all three embodiments the UE maintains the initial CHO configuration upon successful completion of the conditional handover. Furthermore, the UE receives a differential CHO configuration from its new serving cell (here gNB2) and determines an updated CHO configuration based on the stored initial CHO configuration and the received differential CHO configuration. A detailed description in this regard has already been provided in connection with Figure 20 and will not be repeated below.

[0187] Accordingly, the three embodiments differ primarily in the interrelationship of the three base stations involved in the improved conditional handover procedure.

[0188] Furthermore, the following three examples are described focusing on how to generate a differential CHO configuration for gNB1, which was the previous CHO candidate when the UE was located in gNB0. Other aspects are similar to those described elsewhere in this application and will not be repeated below.

[0189] <First Example - Serving Cell Determines All Differential CHO Configurations - Figure 21> According to this first embodiment, the source gNB is primarily responsible for determining the differential CHO configuration parameters for all candidate target cells. In this example, the source eNodeB is responsible for determining the differential CHO configuration parameters for the candidate target cells, while the (differential) execution conditions may be prepared by gNB2, the UE's new serving cell. Therefore, the source gNB requests the CHO configuration parameters from the candidate target cells and then needs appropriate information to determine the differential CHO configuration parameters for each candidate target cell.

[0190] On the other hand, the candidate target cell does not need to be aware that a differential CHO configuration is prepared by the source gNB for the UE instead of a normal CHO configuration, and therefore the behavior of the candidate target cell does not need to be different from when it participates in the preparation of a normal CHO procedure, e.g. as described in detail with respect to the CHO preparation for gNB1 and gNB2 in Figures 8, 9 and 10, or more generally as described according to Figure 20.

[0191] The first embodiment will be described exemplarily with reference to FIG.

[0192] After receiving the CHO execution notification regarding the successful completion of the CHO, the source gNB contacts the candidate target gNB1 to prepare the subsequent CHO procedure between the UE and gNB1, and therefore to request the candidate gNB1's CHO configuration parameters for performing said CHO. For example, the CHO request sent from the source gNB0 to the candidate target gNB1 may be the same (or similar) as the regular CHO request previously used to prepare the (initial) CHO of the candidate targets gNB1 and gNB2.

[0193] The candidate target gNB1 processes the received CHO request (e.g., performs admission control in the normal manner, etc.) and, assuming that gNB1 still allows the UE access to its cell, prepares CHO configuration parameters. These CHO configuration parameters need not necessarily be different from the CHO configuration parameters previously prepared for the initial CHO (when the UE was connected to the source gNB0), but they may be different. In this sense, gNB1 determines updated CHO configuration parameters for the UE to perform a CHO to gNB1 and then transmits the CHO configuration parameters in response to gNB0.

[0194] On the other hand, the candidate gNB1 may decide to discontinue accepting the UE and reject the CHO request. In this case, the source gNB0 receives the rejection from the gNB1 and does not determine differential CHO configuration parameters for the rejected candidate cell. Therefore, the source gNB0 does not transmit differential CHO configuration parameters for the rejected candidate cell to the UE's new serving cell. According to an exemplary variant, the source gNB may then delete the initial CHO configuration stored for the rejected candidate cell.

[0195] Thus, from the perspective of the source gNB0, the differential CHO configuration parameters are determined for the candidate target cells from which the requested cell configuration parameters have been received.

[0196] Assuming that gNB1 still allows the UE access to its cell, source gNB0 receives the requested CHO configuration parameters from gNB1 in response to the transmitted request and therefore has the necessary information to prepare the differential CHO configuration parameters.

[0197] In response, the source gNB0 determines, for the gNB1 from which the requested and received cell configuration parameters were received, differential cell configuration parameters of gNB1, where the differential CHO configuration parameters include configuration parameters of the just-received (updated) CHO configuration parameters that differ from corresponding configuration parameters of the initial CHO configuration parameters of gNB1.

[0198] Source gNB1 stores in memory the previously prepared initial CHO settings for gNB1 from the previous CHO. For example, source gNB1 can identify differences between the parameters, such as updated parameters, new parameters, or removed parameters, by comparing the initial CHO setting parameters with the newly received and updated CHO setting parameters for gNB1. Source gNB0 then prepares differential CHO setting parameters to reflect the determined differences. In one example, the differential CHO setting parameters do not include some or all of the unchanged setting parameters. Therefore, the size of the differential CHO setting parameters can be smaller than the initial CHO setting parameters.

[0199] The source gNB0 then sends the differential CHO configuration parameters of gNB1 to gNB2, which is the serving cell of the UE. The source gNB0 is no longer connected to the UE.

[0200] gNB2 can determine the necessary execution conditions for the CHO prepared for candidate target gNB1. Accordingly, gNB2 prepares a differential CHO configuration for gNB1 that includes the differential CHO configuration parameters obtained from source gNB0 and the newly determined execution conditions.

[0201] In another example, gNB2 may determine a differential execution condition instead of a new execution condition. For example, the source gNB0 has necessary information about the previous execution condition of the CHO between the UE located at the source gNB0 and the candidate target gNB1. The information of the previous execution condition may be transmitted to gNB2, for example, together with the differential CHO configuration parameters of the candidate gNB1. Thus, if the execution condition (or any sub-condition) determined by gNB2 for the differential CHO configuration parameters is the same as the execution condition (or any sub-condition) previously determined (by the source gNB) for the previous CHO, there is no need to transmit the same execution condition to the UE, thereby saving additional signaling overhead.

[0202] In any case, the UE receives the differential CHO configuration for gNB1 and therefore has the necessary information and combines the stored initial CHO configuration (e.g., received in connection with the previous CHO) with the received differential CHO configuration, as already described in detail.

[0203] According to a further exemplary variation of the first embodiment, the CHO execution notification regarding the success of the CHO sent from the target gNB2 to the source gNB0 includes information about the UE's current UE configuration at gNB2. After the conditional handover is successful, the UE's configuration at gNB2 may differ from the previous UE configuration when the UE was located at the source gNB0. Therefore, the current UE configuration at gNB2 is sent by the gNB0 to the candidate target gNB1 together with the CHO request. The candidate target cell gNB1 can use the UE configuration to determine the CHO configuration parameters.

[0204] As an example, the UE configuration information may include one or more of the following:

[0205] The cell ID of one target cell UE ID of a UE located in one target cell gNB2; UE frequency operating parameters Notification of which initial CHO configuration the UE used to perform the CHO procedure In a 5G-compliant variant, the UE configuration information may include one or more of the following fields of the RRCReconfigurationComplete message (which the UE sends to the target cell gNB2 if the CHO is successful) (see also section 6.2.2 of TS 38.331 for the definition of the RRCReconfigurationComplete message): [Table 5]

[0206] One of the important parameters in the above is selectedCondRRCReconfig. For example, information about the current conditional configuration applied by the UE may be important to enable the source gNB to generate updated or differential CHO configurations more efficiently and accurately.

[0207] Optionally, additional information that may be sent from gNB2 to source gNB0 as part of the current UE configuration (e.g., additional information sent along with the CHO execution notification) includes parameters from MeasurementReport, FailureInformation, UEAssistanceInformation, MCGFailureInformation, and other RRC messages.

[0208] According to TS 38.331, clause 6.2.2, the MeasurementReport message is used to report measurement results. According to TS 38.331, clause 6.2.2, the FailureInformation message is used to report errors detected by the UE to the network. According to TS 38.331, clause 6.2.2, the UEAssistanceInformation message is used to report UE assistance information to the network. According to TS 38.331, clause 6.2.2, the MCGFailureInformation message is used to provide information about NR MCG errors detected by the UE.

[0209] <Second Example - Each candidate determines its own differential CHO setting - Figure 22> According to a second embodiment, each candidate target cell determines its own differential CHO configuration. In this example, the candidate target gNB1 determines its own differential CHO configuration parameters, while the (differential) execution conditions can be prepared by the UE's new serving cell, gNB2. Meanwhile, the preparation of differential CHO configurations of multiple candidate target gNBs is coordinated by the UE's new serving cell, gNB2.

[0210] The second embodiment will be described exemplarily with reference to FIG.

[0211] According to one variant, the UE serving cell gNB2 receives differential CHO configuration parameters from the candidate target cells instead of the normal CHO configuration. In response, the UE serving cell gNB2 can distinguish for which candidate target cells it prepares a differential CHO configuration and for which candidate target cells it prepares a normal (full) CHO configuration. To this end, in an exemplary variant, the source gNB0 provides the new serving cell gNB2 with appropriate information about the previous CHO configuration it prepared for the UE, for example, one CHO configuration for gNB1 in this exemplary scenario. In other words, the source gNB0 transmits to the serving cell gNB2 identification information about the candidate target cells for which initial CHO configurations were previously prepared and transmitted to the UE.

[0212] This may be performed by the source gNB0 after receiving a CHO execution notification regarding successful completion of the CHO (as shown in Figure 22), which allows gNB2 to request differential CHO configuration parameters from the notified candidate target cell, here gNB1.

[0213] The candidate target cell gNB1 prepares and returns differential CHO configuration parameters instead of the normal (full) CHO configuration parameters.

[0214] In another exemplary variant, the UE serving cell gNB2 can request normal CHO configuration parameters from the candidate target cell instead of requesting differential CHO configuration parameters. However, since the candidate target cell gNB1 still has the stored initial CHO configuration prepared in the previous CHO, the candidate target cell gNB1 prepares the differential CHO configuration parameters instead of the normal (full) CHO configuration parameters. In this exemplary variant, the source gNB does not need to send information about the previous CHO configuration to the new UE serving cell gNB2.

[0215] According to both variants of the second embodiment, the candidate target cell gNB1 processes the CHO request (e.g., including admission control), and, assuming that gNB1 still allows the UE to access the cell, gNB1 prepares differential CHO configuration parameters for cell access and sends them to the serving cell gNB2. As above, these differential CHO configuration parameters include parameters that differ from the previously prepared initial CHO configuration (the initial CHO configuration created when the UE was connected to the source gNB0).

[0216] On the other hand, the candidate gNB1 may decide to stop accepting the UE and reject the CHO request. In this case, the serving cell gNB2 receives the rejection from the gNB1. Therefore, the serving cell gNB2 also does not send differential CHO configuration parameters for the rejected candidate cell to the UE.

[0217] Assuming that gNB1 still allows the UE to access the cell, serving gNB2 receives differential CHO configuration parameters from gNB1 in response to the transmitted request.

[0218] Additionally, gNB2 may determine the necessary execution conditions for the CHO prepared for candidate target gNB1. Accordingly, gNB2 prepares a differential CHO configuration for gNB1, including the differential CHO configuration parameters obtained from gNB1 and the newly determined execution conditions.

[0219] In another example, the gNB2 may determine a differential execution condition instead of a new execution condition. For example, the source gNB0 has necessary information about the previous execution condition of the CHO between the UE located at the source gNB0 and the candidate target gNB1. The information about the previous execution condition can be transmitted to the gNB2, for example, together with information about the CHO candidate. Thus, if the execution condition (or any sub-condition) determined by the gNB2 for the differential CHO configuration parameter is the same as the execution condition (or any sub-condition) previously determined (by the source gNB) for the previous CHO, there is no need to transmit the same execution condition to the UE, thereby saving additional signaling overhead.

[0220] In any case, as already described in detail, the UE receives the differential CHO configuration for gNB1 and therefore has the necessary information to combine the stored initial CHO configuration (e.g., received in connection with the previous CHO) with the received differential CHO configuration.

[0221] According to a further exemplary variant of the second embodiment, the CHO request sent to the candidate target cell gNB1 includes information about the UE's current UE configuration at gNB2, details about which have already been provided in connection with the first embodiment and will not be repeated here (see also the 5G-compliant variant). The candidate target cell gNB1 can use the UE configuration to determine differential CHO configuration parameters.

[0222] <Third Example - Serving Cell Determines All Differential CHO Configurations - Figure 23> According to the third embodiment, the new serving cell gNB1 primarily determines the differential CHO configurations of all candidate target cells (see FIG. 23).

[0223] On the other hand, as already explained in the first embodiment, the candidate target cell does not need to be aware that it is preparing a differential CHO configuration for the UE instead of a normal CHO configuration, and therefore the behavior of the candidate target cell does not need to be different from when it participates in the preparation of a normal CHO procedure, for example as explained in detail with respect to the CHO preparation for gNB1 and gNB2 according to Figures 8, 9 and 10, or more generally as explained according to Figure 20.

[0224] The third embodiment will now be described by way of example with reference to FIG.

[0225] Considering that the new serving cell gNB2 is responsible for generating the differential CHO configuration, according to one example, the new serving cell is provided with appropriate information about the initial CHO configuration previously prepared for the UE and sent to the UE when the UE was connected to the source gNB0. In response, the source gNB0 can send the previous initial CHO configuration (in this scenario, only the initial CHO configuration of gNB1) to the serving cell gNB2.

[0226] This may be performed by the source gNB0 after receiving a CHO execution notification regarding the successful completion of the CHO (as shown in FIG. 23).

[0227] gNB2 may then contact candidate target gNB1 to prepare a subsequent CHO procedure between the UE and gNB1, and thus to request CHO configuration parameters of candidate gNB1 for performing said CHO. For example, this CHO request sent from serving cell gNB2 to candidate target gNB1 may be identical (or similar) to the regular CHO request previously used to prepare the (initial) CHO for candidate targets gNB1 and gNB2.

[0228] The candidate target gNB1 processes the received CHO request (e.g., performs admission control in the normal manner, etc.) and, assuming that gNB1 still allows the UE access to its cell, prepares CHO configuration parameters. These CHO configuration parameters need not necessarily be, but may be, different from the CHO configuration parameters previously prepared for the initial CHO (when the UE was connected to the source gNB0). In this sense, gNB1 determines updated CHO configuration parameters for the UE to perform a CHO to gNB1 and then transmits the CHO configuration parameters according to the UE's serving cell gNB2.

[0229] On the other hand, the candidate gNB1 may decide to stop accepting the UE and reject the CHO request. In this case, the UE's serving cell gNB2 receives the rejection from gNB1 and does not determine the differential CHO configuration parameters for the rejected candidate cell. Therefore, gNB2 does not send the differential CHO configuration parameters for the rejected candidate cell to the UE.

[0230] Thus, from the perspective of the serving cell gNB2, differential CHO configuration parameters are determined for the candidate target cells from which the requested cell configuration parameters have been received.

[0231] Assuming that gNB1 still allows the UE access to its cell, the UE's serving cell gNB2 receives the requested CHO configuration parameters from gNB1 in response to the transmitted request and therefore has the necessary information to prepare differential CHO configuration parameters.

[0232] For example, as described in the first embodiment, the UE's serving cell gNB2 determines differential cell configuration parameters of gNB1 for gNB1 from which the requested and received cell configuration parameters were received, where the differential CHO configuration parameters include configuration parameters of the just-received (updated) CHO configuration parameters that differ from corresponding configuration parameters of gNB1's initial CHO configuration parameters.

[0233] The UE's serving cell may determine the necessary execution conditions for the new CHO prepared for the candidate target gNB1. Accordingly, gNB2 prepares a differential CHO configuration for gNB1, including the determined differential CHO configuration parameters and the newly determined execution conditions.

[0234] In another example, the gNB2 may determine a differential execution condition instead of a new execution condition. For example, the gNB2 may obtain from the source gNB0 the necessary information about the previous execution condition of the CHO between the UE located at the source gNB0 and the candidate target gNB1 together with the remaining initial CHO configuration (after the CHO execution notification). Thus, if the execution condition (or any sub-condition) determined by the gNB2 for the differential CHO configuration parameter is the same as the execution condition (or any sub-condition) previously determined (by the source gNB) for the previous CHO, there is no need to send the same execution condition to the UE, thereby saving additional signaling overhead.

[0235] In any case, as already described in detail, the UE receives the differential CHO configuration for gNB1 and therefore has the necessary information to combine the stored initial CHO configuration (e.g., received in connection with the previous CHO) with the received differential CHO configuration.

[0236] According to a further exemplary variant of the third embodiment, the CHO request sent to the candidate target cell gNB1 includes information about the UE's current UE configuration at gNB2, details about which have already been provided in connection with the first embodiment and will not be repeated here (see also the 5G-compliant variant). The candidate target cell gNB1 can use the UE configuration to determine differential CHO configuration parameters.

[0237] <Improved CPC procedure> Having provided a detailed description of the improved CHO procedure, an exemplary simplified implementation of the improved conditional cell change (CPC) procedure is described below. The improved CPC procedure is based on the principles described above with respect to the improved CHO procedure and will not be repeated here.

[0238] The improved CPC procedure can be understood as a procedure in which a UE disconnects from a source cell and connects to a candidate target cell (which may be selected from many candidates) when an execution condition is met, i.e., a procedure corresponding to the above-mentioned CHO procedure. The CPC procedure is typically used when a UE is in dual connectivity, for example, when the UE is already configured in a master cell group and a secondary cell group and is connected to at least one primary cell (PCell) in the master cell group and at least one primary cell (PSCell) in the secondary cell group. The improved CPC procedure can be performed by the UE to change the PSCell of the SCG. Accordingly, the source cell and target cell participating in CPC belong to the secondary cell group of the UE in dual connectivity.

[0239] Figure 24 shows an exemplary and simplified implementation of the improved conditional cell change (CPC) procedure, illustrating the exchange of messages between the different participating entities (here UE, gNB0, gNB1, and gNB2) and the steps performed by these entities.

[0240] The improved CPC procedure up to successful completion of the CPC may be the same as (or similar to) the normal CPC procedure, for example, as described above with respect to FIG.

[0241] Important steps and messages for the improved CPC procedure relate to the point after successful completion of CPC, including the UE maintaining the initial CPC configuration, at least for candidate gNB1 (which is the configuration for CPC that was prepared but not executed). Thus, the initial CPC configuration is not deleted from the UE memory at this point. This is in contrast to the legacy CPC procedure (e.g., the procedure described in Figure 11), in which the UE releases all initial CPC configurations upon successful CPC.

[0242] Furthermore, the new PSCell of the UE can then obtain the differential CPC configuration (here, only the differential CPC configuration of gNB1) and provide the differential CPC configuration to the UE. The step of obtaining the differential CPC configuration has already been described in various embodiments in connection with the improved CHO procedure, and will not be repeated here. Briefly, according to a first embodiment, the source gNB is mainly responsible for determining the differential CPC configuration parameters of all candidate target cells and providing them to the new PSCell. According to a second embodiment, each candidate target cell determines its respective differential CPC configuration parameters and provides them to the new PSCell. According to a third embodiment, the new PSCell gNB1 is mainly responsible for determining the differential CPC configurations of all candidate target cells.

[0243] In general, the differential CPC configuration may reflect the difference between the new (updated) CPC configuration of gNB1 (after the previous CPC) and the initial CPC configuration of gNB1. The differential CPC configuration of the candidate target cell may include CPC configuration parameters and / or implementation conditions that are different from the initial CPC configuration of the candidate target cell. The difference may include, for example, updated parameters (e.g., changed values), parameters that may be new parameters, or released parameters (i.e., parameters that are not present in the CPC configuration).

[0244] In one example, the differential CPC configuration may thus be more compact because it does not include some or all of the unchanged elements.

[0245] The UE receives a differential CPC configuration for one candidate target gNB1 from gNB2. The UE generates an updated CPC configuration based on the received differential CPC configuration and the stored initial CPC configuration. In this way, the updated CPC configuration is complete and up-to-date for use as a potential CPC for gNB1 in the future.

[0246] According to another example (not shown), once the CPC to gNB2 is successfully completed, the UE may release the initial CPC configuration for gNB2, since this is not necessary considering that the UE is already successfully connected to gNB2. However, the CPC configuration for other candidate target cells (gNB1 in FIG. 24) is maintained by the UE.

[0247] Similar to what was described for the improved CHO procedure, the improved CPC procedure can also be used when there are more than one candidate target cell, details of which are provided above for the improved CHO procedure and will not be repeated.

[0248] It is also possible that after a successful CPC, one or more of the candidate target cells will not accept the UE, thereby rejecting the new CPC preparation, in which case no differential CPC configuration will be prepared for the rejected target cells.

[0249] Similar to that described for the improved CHO procedure, functionality is provided in the UE to distinguish between legacy CPC behavior (which includes clearing the CPC configuration upon successful CPC completion) and improved CPC behavior (which includes maintaining the CPC configuration as described above). Details are provided above for the improved CHO procedure and will not be repeated.

[0250] <Improved CPA Procedure> Having provided a detailed description of the improved CHO and CPC procedures, we now describe an exemplary and simplified implementation of an improved conditional cell addition (CPA) procedure. The improved CPA procedure is based on the principles described with respect to the improved CHO procedure above and therefore will not be repeated here.

[0251] The improved CPA procedure can be understood as a procedure in which, when a UE satisfies an execution condition, it connects to a candidate target cell (which may be selected from many candidates), and the candidate target cell becomes the primary cell of the UE's secondary cell group that is different from the UE's master cell group. The CPA procedure is typically used when a UE enters dual connectivity, for example, in the process of setting up a secondary cell group and connecting to a primary cell (PSCell) of the secondary cell group. CPA can also be used to add more SCells to the SCG or to create another SCG with another PSCell, but this other SCG is initially in an inactive state.

[0252] Figure 25 shows an exemplary and simplified implementation of such an improved conditional cell addition (CPA) procedure, illustrating the exchange of messages between the different participating entities (here UE, gNB0, gNB1, and gNB2) and the steps performed by these entities.

[0253] The improved CPA procedure leading to successful completion of the CPA can be the same as (or similar to) the regular CPA procedure, for example, as described above in connection with FIG.

[0254] Important steps and messages for the improved CPA procedure relate to the point after successful completion of CPA, including the UE maintaining the initial CPA configuration, at least for candidate gNB1 (which is the configuration for a CPA that was prepared but not executed). Thus, the initial CPA configuration is not deleted from the UE memory at this point. This is in contrast to the legacy CPA procedure (e.g., the procedure described in FIG. 12), in which the UE releases all initial CPA configuration upon successful CPA.

[0255] Also, note that the UE maintains a connection with the serving cell gNB0 (in contrast to the CHO and CPC procedures described above), which becomes a cell in the master cell group, and the target gNB2 becomes a PSCell in the secondary cell group.

[0256] According to an example implementation of the improved CPA procedure, the source cell can obtain a differential CPA configuration (here, only the differential CPA configuration of gNB1) and provide the differential CPA configuration to the UE. The step of obtaining the differential CPA configuration has already been described in various embodiments in relation to the improved CPA procedure, and will not be repeated here. Briefly, according to a first embodiment, the source gNB0 mainly determines the differential CPA configurations of all candidate target cells and provides them to the UE. According to a second embodiment, each candidate target cell determines its own differential CPA configuration parameters and provides them to the source gNB0. According to a third embodiment, gNB1, a new PSCell of the SCG, mainly determines the differential CPA configuration parameters of all candidate target cells and provides them to the source gNB0.

[0257] According to this third embodiment, the differential CPA configuration for gNB1 may be transmitted by gNB0 (as shown in FIG. 25) or transmitted by gNB2 (not shown), and the (differential) execution condition may be determined by gNB0 or gNB2, respectively.

[0258] In general, however, the differential CPA configuration may reflect differences between the new (updated) CPA configuration of gNB1 (after the last CPA) and the initial CPA configuration of gNB1. The differential CPA configuration of a candidate target cell may include CPA configuration parameters and / or execution conditions that differ from the initial CPA configuration of the candidate target cell. The differences may include, for example, updated parameters (e.g., changed values), parameters that may be new parameters, or released parameters (i.e., parameters that are not present in the CPC configuration).

[0259] In one example, the differential CPA configuration may thus be more compact because it does not include some or all of the elements that have not changed.

[0260] The UE receives a differential CPA configuration for one candidate target gNB1 from gNB0 or gNB2. The UE generates an updated CPA configuration based on the received differential CPA configuration and the stored initial CPA configuration. In this way, the updated CPA configuration is complete and up-to-date for use for potential CPA with gNB1 in the future (e.g., when gNB1 becomes an SCell of an SCG, or when gNB1 becomes a PSCell of another, e.g., inactive, SCG, etc.).

[0261] According to another example (not shown), once CPA to gNB2 is successfully completed, the UE may cancel the initial CPA configuration for gNB2, since this is not necessary considering that the UE is already successfully connected to gNB2. However, the CPA configuration for other candidate target cells (gNB1 in FIG. 25) is maintained by the UE.

[0262] Similar to that described for the improved CHO procedure, the improved CPA procedure can also be used when there are more than one candidate target cell, details of which are provided above with respect to the improved CHO procedure and will not be repeated.

[0263] It is also possible that after a successful CPA, one or more of the candidate target cells do not accept the UE, thereby rejecting the preparation of a new CPA, in which case no differential CPA configuration is prepared for the rejected target cells.

[0264] Similar to that described for the improved CHO procedure, functionality is provided in the UE to distinguish between legacy CPA behavior (including de-configuring CPA upon successful CPA completion) and improved CPA behavior (including maintaining CPA configuration as described above). Details are provided above for the improved CHO procedure and will not be repeated.

[0265] Further Aspects According to a first aspect, there is provided a user equipment including: a receiving unit that receives, from a source base station, an initial cell configuration of at least one candidate target cell, each initial cell configuration including cell configuration parameters for each candidate target cell for performing a conditional cell mobility procedure and an execution condition for when to perform the conditional cell mobility procedure for each candidate target cell; a circuit in the UE that, when the execution condition is satisfied for a target cell among the at least one candidate target cell, performs the conditional cell mobility procedure for the target cell based on the cell configuration parameters of the target cell; and, when the conditional cell mobility procedure between the UE and the target cell is completed, maintains the received initial cell configuration of the at least one candidate target cell.

[0266] According to a second aspect provided in addition to the first aspect, a receiver receives differential cell configurations for one or more of the at least one candidate target cell from a target base station that controls the target cell. For each received differential cell configuration, the circuit generates an updated cell configuration based on both the differential cell configuration and the initial cell configuration. In any embodiment, the differential cell configuration includes cell configuration parameters and / or execution conditions that differ from the initial cell configuration of each candidate target cell. Furthermore, in any embodiment, the differential cell configuration includes one or a combination of the following cell configuration parameters:

[0267] Different candidate cell lists, Different cell IDs, · Different carrier frequencies.

[0268] Additionally, in any embodiment, the differential cell configuration includes one or more different sub-conditions of the performance condition, including different measurement quantities or measurement thresholds of the performance condition.

[0269] According to a third aspect provided in addition to the second aspect, the circuit cancels an initial cell configuration for a candidate target cell for which a differential cell configuration has not been received from the target base station.

[0270] According to a fourth aspect provided in addition to any one of the first to third aspects, maintaining the received initial cell configuration comprises not deleting the received initial cell configuration. In any embodiment, maintaining the received initial cell configuration further comprises determining that the initial cell configuration is maintained in response to successful completion of the conditional cell mobility procedure based on:

[0271] Preconfiguration information stored in the UE, optionally the preconfiguration information being received from a source base station; Information that the UE receives from the target cell during the conditional cell mobility procedure According to a fifth aspect provided in addition to any one of the first to fourth aspects, the conditional cell mobility procedure is one of the following:

[0272] A conditional handover, in which, if an execution condition is met, the UE disconnects from a source cell of a source base station and connects to a candidate target cell, optionally, the source cell and the target cell belong to the same master group of cells of the UE; A conditional cell change, in which, when an execution condition is met, the UE disconnects from the source cell and connects to a candidate target cell, and the source cell and the candidate target cell belong to a secondary group of cells of the UE that is different from the master group of cells of the UE; Conditional cell addition, where if the execution condition is met, the UE connects to a candidate target cell, which is a primary cell of a secondary group of the UE's cell that is different from the master group of the UE's cell.

[0273] According to a sixth aspect provided in addition to any one of the first to fifth aspects, the UE performs one or more of the following steps:

[0274] storing the received initial cell configuration of at least one candidate target cell; determining, for each of the at least one candidate target cell, whether an execution condition for performing a conditional cell mobility procedure for each candidate target cell is met; Sending a measurement report to the source base station including results of measurements performed by the UE to assist the source base station in the conditional cell mobility procedure.

[0275] In any embodiment, the cell configuration parameters of the initial cell configuration include one or more of the following:

[0276] Radio resource configuration of candidate target cells, such as resource block and physical channel configuration, Security configuration of candidate target cells, Dual connectivity information such as master cell group information, secondary cell group information, etc. Measurement configuration of candidate target cells, Mobility settings.

[0277] Furthermore, in any embodiment, the execution condition regarding when to perform the conditional cell mobility procedure includes one or more sub-conditions, and the execution condition is fulfilled when one or all of the sub-conditions are fulfilled. Optionally, the sub-conditions relate to communication quality of one or more of the source cell of the source base station and the candidate target cells associated with the execution condition.

[0278] According to a seventh aspect, there is provided a base station comprising: a transmitter unit of the base station transmits to a user equipment (UE) an initial cell configuration of at least one candidate target cell, each initial cell configuration comprising cell configuration parameters of each candidate target cell for performing a conditional cell mobility procedure, and comprising an execution condition regarding when to perform the conditional cell mobility procedure between the UE and each candidate target cell; a receiver unit of the base station receives, from a target base station of a target cell among the at least one candidate target cell, a notification regarding successful completion of the conditional cell mobility procedure between the UE and the target cell; after receiving the notification regarding successful completion of the conditional cell mobility procedure, the transmitter sends, to one or more candidate target cells among the candidate target cells for which the conditional cell mobility procedure has not been performed, a request to request cell configuration parameters of each candidate target cell for performing the conditional cell mobility procedure between the UE and each candidate target cell; the receiver receiving requested cell configuration parameters from one or more candidate target cells in response to the transmitted request; the base station circuitry determines, for each of the one or more candidate target cells for which requested and received cell configuration parameters were received, differential cell configuration parameters for each candidate target cell, the differential cell configuration parameters including cell configuration parameters that differ from cell configuration parameters of the initial cell configuration of each candidate target cell; The transmitter transmits differential cell configuration parameters of one or more candidate target cells to a target base station of the target cell.

[0279] According to an eighth aspect provided in addition to the seventh aspect, the receiver receives, from a target base station of the target cell, configuration parameters of a UE connected to the target base station. In an optional embodiment, the configuration parameters of the UE include one or more of a cell ID of the target cell, a UE ID of a UE located in the target cell, frequency operation parameters of the UE, and an indication of which initial cell configuration the UE used to perform the conditional cell mobility procedure. In a further optional embodiment, the configuration parameters of the UE are received together with an indication of successful completion of the conditional cell mobility procedure.

[0280] Furthermore, when sending the request for the cell configuration parameters to the one or more candidate target cells, the transmitter also sends the received configuration parameters of the UE to the one or more candidate target cells.

[0281] According to a ninth aspect provided in addition to the seventh or eighth aspect, if the receiving unit receives a rejection of the request from a candidate target cell instead of the requested cell configuration parameters in response to the transmitted request, the base station: Without determining the differential cell setting parameters, Do not send different cell configuration parameters to the target cell, Optionally, remove the initial cell configuration of rejected candidate target cells.

[0282] According to a tenth aspect provided in addition to any one of the seventh to ninth aspects, the transmitter transmits, to a target base station of the target cell, identification information of at least one candidate target cell that has transmitted an initial cell configuration to the UE.

[0283] According to an eleventh aspect provided in addition to any one of the seventh to tenth aspects, before transmitting an initial cell configuration of at least one candidate target cell, the transmitter sends to each of the at least one candidate target cell a request requesting cell configuration parameters of each candidate target cell for performing a conditional cell mobility procedure between the UE and each candidate target cell, and in any embodiment the transmitter sends together with the request the configuration parameters of the UE connected to the base station; The circuitry determines an execution condition regarding when to perform a conditional cell mobility procedure between the UE and each candidate target cell.

[0284] According to a twelfth aspect, there is provided a base station comprising: a transmitter unit of the base station transmits, to a source base station, initial cell configuration parameters for performing a conditional cell mobility procedure between a user equipment (UE) and a base station serving a target cell; a circuit of the base station performs the conditional cell mobility procedure with the UE based on the transmitted initial cell configuration parameters, thereby connecting the UE to the target cell; a circuit of the base station obtains differential cell configuration parameters of one or more candidate target cells for performing the conditional cell mobility procedure between the UE and each of the one or more candidate target cells; the differential cell configuration parameters for the candidate target cells include parameters that are different from the initial cell configuration parameters for performing the conditional cell mobility procedure between the UE and each of the candidate target cells; and a circuit that determines, for each of the one or more candidate target cells, an execution condition for when to perform the conditional cell mobility procedure between the UE and each of the candidate target cells. The transmitter unit transmits a differential cell configuration for each of the one or more candidate target cells to the UE, the differential cell configuration including the determined differential cell configuration parameters for the one or more candidate target cells and the determined execution condition.

[0285] According to a thirteenth aspect provided in addition to the twelfth aspect, obtaining differential cell configuration parameters for one or more candidate target cells includes receiving the differential cell configuration parameters from a source base station.

[0286] According to a fourteenth aspect provided in addition to the twelfth or thirteenth aspect, obtaining differential cell configuration parameters of one or more candidate target cells includes: receiving, from the source base station, an identity of at least one candidate target cell for a conditional cell mobility procedure to be performed between the UE and each candidate target cell; for each of the identified at least one candidate target cell; sending a request to request cell configuration parameters for performing a conditional cell mobility procedure between the UE and each candidate target cell; receiving, in response to the transmitted request, from each candidate target cell, differential cell configuration parameters for each candidate target cell.

[0287] According to a fifteenth aspect provided in addition to any one of the twelfth to fourteenth aspects, the obtaining of differential cell configuration parameters for one or more candidate target cells includes: receiving, from the source base station, identification information for at least one candidate target cell before performing the conditional cell mobility procedure to the base station, and receiving initialization parameters for performing the conditional cell mobility procedure between the UE and each candidate target cell; for each of the identified at least one candidate target cell; sending, to each candidate target cell, a request requesting cell configuration parameters for performing a conditional cell mobility procedure between the UE and each candidate target cell; receiving, in response to the transmitted request, from each candidate target cell, cell configuration parameters for each requested candidate target cell; determining differential cell configuration parameters for each candidate target cell based on the requested cell configuration parameters received from each candidate target cell and the initial configuration parameters received from the source base station.

[0288] According to a 16th aspect provided in addition to any one of the 12th to 15th aspects, a transmitter transmits a notification to a source base station regarding successful completion of a conditional cell mobility procedure between the UE and the base station.

[0289] In an optional embodiment, the transmitter transmits configuration parameters of the UE connecting to the base station to the source base station. Further, the configuration parameters of the UE include one or more of a cell ID of the target cell, a UE ID of the UE connecting to the base station, frequency operation parameters of the UE, and an indication of which initial cell configuration the UE used to perform the conditional cell mobility procedure. As a further option, the configuration parameters of the UE are transmitted together with an indication of successful completion of the conditional cell mobility procedure.

[0290] According to a 17th aspect provided in addition to the 12th to 16th aspects, a transmitter transmits initial cell configuration parameters to the other base station for performing a conditional cell mobility procedure between the other UE and the base station. A receiver receives a request from the other base station requesting cell configuration parameters for performing the conditional cell mobility procedure between the other UE and the base station, and optionally, the receiver also receives configuration parameters for the UE. A circuit determines updated cell configuration parameters for performing the conditional cell mobility procedure between the other UE and the base station. The circuit determines differential cell configuration parameters based on both the initial cell configuration parameters and the updated cell configuration parameters. The differential cell configuration parameters include parameters that are different from the initial cell configuration parameters and the updated cell configuration parameters.

[0291] According to an eighteenth aspect, there is provided a method, the method including the following steps performed by a User Equipment (UE):

[0292] receiving, from the source base station, an initial cell configuration of at least one candidate target cell, wherein each initial cell configuration includes cell configuration parameters for each candidate target cell for performing a conditional cell mobility procedure between the UE and each candidate target cell, and an execution condition for when to perform the conditional cell mobility procedure for each candidate target cell; performing a conditional cell mobility procedure in the target cell based on cell configuration parameters of the target cell when an execution condition of the target cell among the at least one candidate target cell is satisfied; and maintaining the received initial cell configuration of the at least one candidate target cell upon successful completion of the conditional cell mobility procedure between the UE and the target cell.

[0293] According to a nineteenth aspect, there is provided a method comprising the following steps executed by a base station:

[0294] sending to a User Equipment (UE) an initial cell configuration of at least one candidate target cell, each initial cell configuration comprising cell configuration parameters for each candidate target cell for performing a conditional cell mobility procedure between the UE and each candidate target cell, and an execution condition for when to perform the conditional cell mobility procedure between the UE and each candidate target cell; receiving a notification from a target base station of a target cell among the at least one candidate target cell regarding successful completion of a conditional cell mobility procedure between the UE and the target cell; After receiving notification about the successful completion of the conditional cell mobility procedure, sending a request to one or more candidate target cells among the candidate target cells for which a conditional cell mobility procedure has not been performed, requesting cell configuration parameters for each of the candidate target cells for performing a conditional cell mobility procedure between the UE and each of the candidate target cells; receiving requested cell configuration parameters from one or more candidate target cells in response to the transmitted request; for each of one or more candidate target cells for which requested and received cell configuration parameters have been received, determining differential cell configuration parameters for each candidate target cell, the differential cell configuration parameters including cell configuration parameters that differ from cell configuration parameters of the initial cell configuration of each candidate target cell; Sending differential cell configuration parameters of one or more candidate target cells to a target base station of the target cell.

[0295] According to a twentieth aspect, there is provided a message including the following steps performed by a base station:

[0296] sending, to a source base station, initial cell configuration parameters for performing a conditional cell mobility procedure between a user equipment (UE) and a base station serving the target cell; performing a conditional cell mobility procedure with the UE based on the transmitted initial cell configuration parameters to connect the UE to the target cell; obtaining differential cell configuration parameters of one or more candidate target cells usable for performing a conditional cell mobility procedure between the UE and each of the one or more candidate target cells, wherein the differential cell configuration parameters of the candidate target cells comprise parameters that are different from initial cell configuration parameters for performing the conditional cell mobility procedure between the UE and each of the candidate target cells; determining, for each of the one or more candidate target cells, an execution condition regarding when to perform a conditional cell mobility procedure between the UE and each candidate target cell; sending to the UE a differential cell configuration for each of the one or more candidate target cells, the differential cell configuration including the determined differential cell configuration parameters for the one or more candidate target cells and the determined execution conditions.

[0297] According to a twenty-first aspect, there is provided an integrated circuit for controlling processing of a user equipment (UE), the processing comprising: receiving, from the source base station, an initial cell configuration of at least one candidate target cell, wherein each initial cell configuration includes cell configuration parameters for each candidate target cell for performing a conditional cell mobility procedure between the UE and each candidate target cell, and an execution condition for when to perform the conditional cell mobility procedure for each candidate target cell; performing a conditional cell mobility procedure in the target cell based on cell configuration parameters of the target cell when an execution condition of the target cell among the at least one candidate target cell is satisfied; and upon successful completion of the conditional cell mobility procedure between the UE and the target cell, maintaining the received initial cell configuration of at least one candidate target cell, wherein the above steps are performed by the UE.

[0298] According to a twenty-second aspect, there is provided an integrated circuit for controlling processing of a base station, the processing comprising: sending to a User Equipment (UE) an initial cell configuration of at least one candidate target cell, each initial cell configuration including cell configuration parameters for each candidate target cell for performing a conditional cell mobility procedure between the UE and each candidate target cell, and an execution condition for when to perform the conditional cell mobility procedure between the UE and each candidate target cell; receiving a notification from a target base station of a target cell among the at least one candidate target cell regarding successful completion of a conditional cell mobility procedure between the UE and the target cell; After receiving notification about the successful completion of the conditional cell mobility procedure, sending a request to one or more candidate target cells among the candidate target cells for which a conditional cell mobility procedure has not been performed, requesting cell configuration parameters for each of the candidate target cells for performing a conditional cell mobility procedure between the UE and each of the candidate target cells; receiving requested cell configuration parameters from one or more candidate target cells in response to the transmitted request; for each of one or more candidate target cells for which requested and received cell configuration parameters have been received, determining differential cell configuration parameters for each candidate target cell, the differential cell configuration parameters including cell configuration parameters that differ from cell configuration parameters of the initial cell configuration of each candidate target cell; sending differential cell configuration parameters of one or more candidate target cells to a target base station of the target cell, wherein the steps are performed by the base station.

[0299] According to a twenty-third aspect, there is provided an integrated circuit for controlling processing of a base station, the processing comprising: transmitting, to a source base station, initial cell configuration parameters for performing a conditional cell mobility procedure between a user equipment (UE) and a base station serving a target cell; Attaching the UE to the target cell by performing a conditional cell mobility procedure with the UE based on the transmitted initial cell configuration parameters; obtaining differential cell configuration parameters of one or more candidate target cells for performing a conditional cell mobility procedure between the UE and each of the one or more candidate target cells, wherein the differential cell configuration parameters of the candidate target cells include parameters different from initial cell configuration parameters for performing the conditional cell mobility procedure between the UE and each of the candidate target cells; determining, for each of the one or more candidate target cells, an execution condition regarding when to perform a conditional cell mobility procedure between the UE and each candidate target cell; The method includes transmitting to the UE a differential cell configuration for each of the one or more candidate target cells, the differential cell configuration including the determined differential cell configuration parameters for the one or more candidate target cells and the determined execution conditions, the steps being performed by the base station.

[0300] Further variations, including hardware and software implementations of the present disclosure The present disclosure can be realized by software, hardware, or software interfacing with hardware. Each functional block used in the description of each embodiment above can be partially or entirely realized by an LSI such as an integrated circuit, and each process described in each embodiment can be partially or entirely controlled by the same LSI or a combination of LSIs. The LSI may be formed as an individual chip, or a single chip may be formed to include some or all of the functional blocks. The LSI may also include data input / output devices coupled thereto. Here, LSIs may be referred to as ICs (integrated circuits), system LSIs, super LSIs, or ultra LSIs depending on their level of integration. However, integrated circuits are not limited to LSIs and may be realized using dedicated circuits, general-purpose processors, or application-specific processors. Furthermore, field programmable gate arrays (FPGAs), which allow reconfiguration of the connections and settings of circuit cells arranged within an LSI or reconfigurable processors that can be programmed after fabrication, may also be used. The present disclosure can be realized using digital or analog processing. As a result of advances in semiconductor technology and other derivative technologies, if future integrated circuit technologies replace LSI, functional blocks can be integrated using future integrated circuit technologies. Biotechnology is also applicable.

[0301] The present disclosure may be implemented by any type of apparatus, device or system having communication capabilities, referred to as a communications apparatus.

[0302] A communication device may include a transceiver and processing / control circuitry. The transceiver may include and / or function as a receiver and a transmitter. The transceiver as a transmitter and receiver may include a Radio Frequency (RF) module including an amplifier, an RF modulator / demodulator, etc., and one or more antennas.

[0303] Some non-limiting examples of such communication devices include telephones (e.g., mobile (cell) phones, smartphones), tablets, personal computers (PCs) (e.g., laptops, desktops, netbooks), cameras (e.g., digital still / video cameras), digital players (digital audio / video players), wearable devices (e.g., wearable cameras, smart watches, tracking devices), game consoles, digital book readers, telehealth / telemedicine (remote health and remote medical) devices, and vehicles (e.g., automobiles, airplanes, ships) that provide communication capabilities, and various combinations thereof.

[0304] The communications apparatus is not limited to being portable or mobile, but may include any type of apparatus, device or system that is non-portable or fixed, such as smart home devices (e.g., appliances, lighting, smart meters, control panels), vending machines and any other "thing" in an "Internet of Things (IoT)" network.

[0305] Communications may include, for example, exchanging data via cellular systems, wireless LAN systems, satellite systems, and the like, as well as various combinations thereof.

[0306] A communications apparatus may include devices such as a controller or a sensor coupled to the communications device to perform the communications functions described in this disclosure. For example, a communications apparatus may include a controller or a sensor that generates control or data signals used by the communications device to perform the communications functions of the communications apparatus.

[0307] Additionally, the communications apparatus may include infrastructure facilities such as, for example, base stations, access points, and any other apparatus, device, or system that communicates with or controls apparatus such as those in the non-limiting examples above.

[0308] (control signal) In this disclosure, the downlink control signal (information) related to this disclosure may be a signal (information) transmitted via a PDCCH of a physical layer, or may be a signal (information) transmitted via a MAC Control Element (CE) or RRC of a higher layer. The downlink control signal may be a predefined signal (information).

[0309] The uplink control signal (information) related to the present disclosure may be a signal (information) transmitted via a PUCCH in the physical layer or a signal (information) transmitted via a MAC CE or RRC in a higher layer. The uplink control signal may also be a predefined signal (information). The uplink control signal may be replaced with uplink control information (UCI), first-stage sidelink control information (SCI), or second-stage SCI.

[0310] (base station) In the present disclosure, a base station may be, for example, a Transmission Reception Point (TRP), a cluster head, an access point, a Remote Radio Head (RRH), an eNodeB (eNB), a gNodeB (gNB), a Base Station (BS), a Base Transceiver Station (BTS), a base unit, or a gateway. In addition, a terminal may be employed instead of a base station in sidelink communication. The base station may be a relay device that relays communication between an upper node and a terminal. The base station may be a roadside unit.

[0311] (uplink / downlink / sidelink) The present disclosure may be applied to any of the uplink, downlink, and sidelink.

[0312] The present disclosure may apply, for example, to uplink channels such as PUSCH, PUCCH, and PRACH, downlink channels such as PDSCH, PDCCH, and PBCH, and sidelink channels such as the Physical Sidelink Shared Channel (PSSCH), the Physical Sidelink Control Channel (PSCCH), and the Physical Sidelink Broadcast Channel (PSBCH).

[0313] The PDCCH, PDSCH, PUSCH, and PUCCH are examples of a downlink control channel, a downlink data channel, an uplink data channel, and an uplink control channel, respectively. The PSCCH and PSSCH are examples of a sidelink control channel and a sidelink data channel, respectively. The PBCH and PSBCH are examples of a broadcast channel, and the PRACH is an example of a random access channel. (Data channel / Control channel) The present disclosure may be applied to both data channels and control channels. The channels in this disclosure may be replaced with data channels including PDSCH, PUSCH, and PSSCH, and / or control channels including PDCCH, PUCCH, PBCH, PSCCH, and PSBCH.

[0314] (reference signal) In this disclosure, a reference signal is a signal known to both a base station and a mobile station, and each reference signal may be referred to as a reference signal (RS) or, in some cases, a pilot signal. A reference signal may be any of a DMRS, a Channel State Information-Reference Signal (CSI-RS), a Tracking Reference Signal (TRS), a Phase Tracking Reference Signal (PTRS), a Cell-specific Reference Signal (CRS), and a Sounding Reference Signal (SRS).

[0315] (time interval) In the present disclosure, the time resource unit is not limited to one or a combination of a slot and a symbol, and may be a time resource unit such as a frame, a superframe, a subframe, a slot, a time slot subslot, a minislot, a symbol, an Orthogonal Frequency Division Multiplexing (OFDM) symbol, a Single Carrier-Frequency Division Multiplexing Access (SC-FDMA) symbol, or other time resource unit. The number of symbols included in one slot is not limited to any of the numbers of symbols exemplified in the above embodiment(s), and may be other numbers of symbols.

[0316] (frequency band) The present disclosure may be applied to both licensed and unlicensed bands.

[0317] (communication) The present disclosure may be applied to communication between a base station and a terminal (Uu link communication), communication between terminals (sidelink communication), and vehicle-to-everything (V2X) communication. The channels in the present disclosure may be replaced with PSCCH, PSSCH, Physical Sidelink Feedback Channel (PSFCH), PSBCH, PDCCH, PUCCH, PDSCH, PUSCH, and PBCH.

[0318] The present disclosure may also be applied to terrestrial networks or non-terrestrial networks (NTNs) that use satellites or high altitude pseudo satellites (HAPSs). The present disclosure may also be applied to networks with large cell sizes and terrestrial networks with large delays compared to the symbol length or slot length, such as ultra-wideband transmission networks.

[0319] (antenna port) An antenna port refers to a logical antenna (antenna group) formed by one or more physical antennas (multiple antennas are possible). That is, an antenna port does not necessarily refer to one physical antenna, but may refer to an array antenna formed by multiple antennas. For example, the number of physical antennas forming an antenna port is not defined. Instead, an antenna port is defined as the smallest unit by which a terminal can transmit a reference signal. An antenna port may also be defined as the smallest unit for multiplying a weight of a precoding vector.

[0320] Furthermore, the various embodiments may be implemented by means of software modules, which are executed by a processor or directly in hardware. A combination of software modules and hardware implementations may also be possible. The software modules may be stored on any kind of computer-readable storage medium, for example RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROM, DVD, etc. Furthermore, it should be noted that individual features of the different embodiments may be the subject of another embodiment, either individually or in any combination.

[0321] Those skilled in the art will recognize that numerous changes and / or modifications may be made to the present disclosure as set forth in the specific embodiments, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

1. A communication device, a receiver configured to receive, during operation, from a source base station, an initial cell configuration of at least one candidate target cell, each initial cell configuration including cell configuration parameters and a condition for performing a conditional cell mobility procedure; and a circuit for, during operation, performing the conditional cell mobility procedure based on the cell configuration parameters of a target cell if the execution condition of the target cell among the at least one candidate target cell is satisfied; and wherein, in operation, the circuitry maintains the received initial cell configuration of the at least one candidate target cell upon successful completion of the conditional cell mobility procedure. Communication equipment.

2. The receiver, in operation, receives differential cell configurations of one or more candidate target cells from a target base station that controls the target cells; the circuitry, in operation, generates an updated cell configuration for each received differential cell configuration based on the differential cell configuration and the initial cell configuration; Optionally, the differential cell configuration comprises different cell configuration parameters and / or implementation conditions than the initial cell configuration of each of the candidate target cells; Optionally, the differential cell configuration comprises one or a combination of the following cell configuration parameters: - different candidate cell lists, - different cell IDs, - different carrier frequencies, Optionally, the differential cell configuration comprises one or more different sub-conditions of the performance condition, comprising different measurement quantities or measurement thresholds of the performance condition. The communication device according to claim 1 .

3. In operation, the circuitry cancels the initial cell configuration for a candidate target cell that has not received a differential cell configuration from the target base station. The communication device according to claim 2 .

4. maintaining the received initial cell configuration includes not deleting the received initial cell configuration; Optionally, maintaining the received initial cell configuration based on further comprising determining that the initial cell configuration is maintained upon successful completion of the conditional cell mobility procedure. Pre-configuration information stored in the communication device, optionally the pre-configuration information is received from the source base station; - information obtained by the communications device from the target cell during the conditional cell mobility procedure; The communication device according to claim 1 .

5. The conditional cell mobility procedure is one of the following: a conditional handover, in which, upon fulfillment of the execution condition, the communication device disconnects from a source cell of the source base station and connects to a candidate target cell, optionally the source cell and the target cell belonging to the same master group of cells of the communication device; a conditional cell change, where, upon fulfillment of the execution condition, the communication device disconnects from the source cell and connects to a candidate target cell, the source cell and the candidate target cell belonging to a secondary group of cells of the communication device that is different from a master group of cells of the communication device; Conditional cell addition, wherein the communication device connects to a candidate target cell when the execution condition is met, and the candidate target cell is a primary cell of a secondary group of cells of the communication device that is different from a master group of cells of the communication device. The communication device according to claim 1 .

6. The communication device storing the received initial cell configuration of the at least one candidate target cell; determining, for each of the at least one candidate target cell, whether the execution condition for performing the conditional cell mobility procedure for each of the candidate target cells is satisfied; sending a measurement report to the source base station, the measurement report including results of measurements performed by the communication device to assist the source base station in the conditional cell mobility procedure; Execute one or more of the following: Optionally, the cell configuration parameters of the initial cell configuration include: - Radio resource configuration of the candidate target cell, such as resource block, physical channel configuration, etc. - security settings of said candidate target cells; - Dual connectivity information such as master cell group information, secondary cell group information, etc. - measurement configuration of said candidate target cells; - Mobility settings, and Optionally, the execution condition of the conditional cell mobility procedure includes one or more sub-conditions, one or all of which must be satisfied for the execution condition to be satisfied, and optionally, the sub-conditions relate to communication qualities of a source cell of the source base station and one or more of the candidate target cells with respect to the execution condition; The communication device according to claim 1 .

7. A base station, a transmitter configured, during operation, to transmit to the communication device an initial cell configuration of at least one candidate target cell, each initial cell configuration including cell configuration parameters and a condition for performing a conditional cell mobility procedure; a receiver configured, during operation, to receive a notification from a target base station of a target cell of the at least one candidate target cell regarding successful completion of the conditional cell mobility procedure; after receiving notification regarding successful completion of said conditional cell mobility procedure; the transmitter, in operation, is operable to send a request to one or more of the candidate target cells for which the conditional cell mobility procedure has not been performed, requesting cell configuration parameters for each of the candidate target cells; a receiver, in operation, for receiving the requested cell configuration parameters from the one or more candidate target cells; the base station circuitry, in operation, determines differential cell configuration parameters for each of the candidate target cells, the differential cell configuration parameters including cell configuration parameters that differ from the cell configuration parameters of the initial cell configuration for each of the candidate target cells; the transmitter, in operation, transmits the differential cell configuration parameters of the one or more candidate target cells to a target base station of the target cell; Base station.

8. In operation, the receiver receives, from the target base station of the target cell, configuration parameters of the communication device in connection with the target base station, optionally the configuration parameters of the communication device including one or more of a cell ID of the target cell, a communication device ID of the communication device located in the target cell, frequency operation parameters of the communication device, and an indication regarding which initial cell configuration the communication device used to perform the conditional cell mobility procedure, and optionally the configuration parameters of the communication device are received together with an indication regarding successful completion of the conditional cell mobility procedure; the transmitter, when operating and transmitting the request for the cell configuration parameters to the one or more candidate target cells, also transmits the configuration parameters received by the communication device to the one or more candidate target cells. The base station of claim 7.

9. If the receiver receives a rejection of the request from a candidate target cell instead of the requested cell configuration parameters, the base station, in operation, Without determining the differential cell setting parameters, not transmitting differential cell configuration parameters to the target cell; Optionally, deleting the initial cell configuration of the rejected candidate target cell. The base station of claim 7.

10. The transmitter, in operation, transmits, to the target base station of the target cell, identification information of the at least one candidate target cell for which an initial cell configuration has been transmitted to the communication device. A base station according to any one of claims 7 to 9.

11. before transmitting the initial cell configuration of the at least one candidate target cell; In operation, the transmitter is configured to transmit to each of the at least one candidate target cell a request for cell configuration parameters of the respective candidate target cell for performing the conditional cell mobility procedure between the communication device and each of the candidate target cells, and optionally transmit configuration parameters of the communication device connected to the base station together with the request; The circuitry, in operation, determines the execution condition of the conditional cell mobility procedure between the communication device and each of the candidate target cells. The base station of claim 7.

12. a transmitter configured, in operation, to transmit initial cell configuration parameters of a conditional cell mobility procedure to a source base station; a circuit for, in operation, performing the conditional cell mobility procedure with the communication device based on the transmitted initial cell configuration parameters; In operation, the circuitry obtains differential cell configuration parameters of one or more candidate target cells for performing the conditional cell mobility procedure, the differential cell configuration parameters including parameters that are different from the initial cell configuration parameters; In operation, the circuitry determines, for each of the one or more candidate target cells, a condition for performing the conditional cell mobility procedure; and wherein the transmitter, in operation, transmits to the communication device a differential cell configuration for each of the one or more candidate target cells, the differential cell configuration including the determined differential cell configuration parameters and the determined execution condition. Base station.

13. obtaining the differential cell configuration parameters for the one or more candidate target cells includes receiving the differential cell configuration parameters from the source base station. The base station of claim 12.

14. The obtaining of the differential cell configuration parameters of the one or more candidate target cells includes: receiving from the source base station identification information for at least one candidate target cell of the conditional cell mobility procedure to be performed between the communications device and each of the candidate target cells; For each of the identified at least one candidate target cell: sending a request for cell configuration parameters of the conditional cell mobility procedure; receiving, from each of the candidate target cells, the differential cell configuration parameters for each of the candidate target cells; Including, The base station of claim 12.

15. The obtaining of the differential cell configuration parameters for the one or more candidate target cells includes: receiving, from the source base station, identification information for at least one candidate target cell prior to performing the conditional cell mobility procedure to the base station, and receiving initialization parameters for the conditional cell mobility procedure; For each of the identified at least one candidate target cell: sending a request to each of the candidate target cells requesting cell configuration parameters for the conditional cell mobility procedure; receiving the cell configuration parameters for each of the requested candidate target cells from each of the candidate target cells; determining the differential cell configuration parameters for each of the candidate target cells based on the requested cell configuration parameters received from each of the candidate target cells and the initial configuration parameters received from the source base station; Including, The base station of claim 12.

16. The transmitter, upon operation, transmits a notification to the source base station regarding successful completion of the conditional cell mobility procedure; Optionally, the transmitter, in operation, transmits configuration parameters of the communication device connected to the base station to the source base station, optionally the configuration parameters of the communication device including one or more of a cell ID of the candidate target cell, a communication device ID of the communication device connected to the base station, frequency operation parameters of the communication device, and a notification regarding which initial cell configuration the communication device used to perform the conditional cell mobility procedure, and optionally the configuration parameters of the communication device are transmitted together with a notification regarding successful completion of the conditional cell mobility procedure. The base station of claim 12.

17. The transmitter, in operation, transmits the initial cell configuration parameters of the conditional cell mobility procedure to another base station; the receiver, in operation, receives from the other base station a request for cell configuration parameters for performing the conditional cell mobility procedure, and optionally the receiver also receives configuration parameters of the communication device; The circuitry, in operation, determines updated cell configuration parameters for the conditional cell mobility procedure; and wherein the circuit, in operation, determines differential cell configuration parameters based on both the initial cell configuration parameters and the updated cell configuration parameters, the differential cell configuration parameters including parameters that are different from the initial cell configuration parameters and the updated cell configuration parameters. The base station of claim 12.

18. 1. A method performed by a communication device, comprising: receiving, from the source base station, an initial cell configuration for at least one candidate target cell, each initial cell configuration including cell configuration parameters for each candidate target cell and a condition for performing a conditional cell mobility procedure; If the execution condition for a target cell among the at least one candidate target cell is satisfied, executing the conditional cell mobility procedure in the target cell based on the cell configuration parameters of the target cell; maintaining the received initial cell configuration of the at least one candidate target cell upon successful completion of the conditional cell mobility procedure; A method comprising:

19. A method comprising the steps of: - transmitting to the communication device an initial cell configuration for at least one candidate target cell, each initial cell configuration including cell configuration parameters for each candidate target cell and a condition for performing a conditional cell mobility procedure; receiving a notification from a target base station of a target cell of the at least one candidate target cell regarding successful completion of the conditional cell mobility procedure; after receiving the notification regarding successful completion of the conditional cell mobility procedure; - sending a request to one or more of the candidate target cells for which the conditional cell mobility procedure has not been performed, requesting cell configuration parameters for each of the candidate target cells for performing the conditional cell mobility procedure; receiving the requested cell configuration parameters from the one or more candidate target cells; - determining differential cell configuration parameters for each of the candidate target cells, the differential cell configuration parameters comprising cell configuration parameters that differ from cell configuration parameters of the initial cell configuration for each of the candidate target cells; transmitting the differential cell configuration parameters of the one or more candidate target cells to a target base station of the target cell; A method comprising:

20. A method comprising the steps of: sending initial cell configuration parameters of the conditional cell mobility procedure to a source base station; performing the conditional cell mobility procedure with the communication device based on the transmitted initial cell configuration parameters; obtaining differential cell configuration parameters of one or more candidate target cells for performing the conditional cell mobility procedure, wherein the differential cell configuration parameters of the candidate target cells include parameters different from initial cell configuration parameters for performing the conditional cell mobility procedure; determining, for each of the one or more candidate target cells, a condition for performing the conditional cell mobility procedure; sending to the communication device a differential cell configuration for each of the one or more candidate target cells, the differential cell configuration including the determined differential cell configuration parameters and the determined execution condition; A method comprising:

21. 1. An integrated circuit that, in operation, controls the processing of a communications device, said processing comprising: receiving, from the source base station, an initial cell configuration for at least one candidate target cell, each initial cell configuration including cell configuration parameters for each candidate target cell and a condition for performing a conditional cell mobility procedure; If the execution condition for a target cell among the at least one candidate target cell is satisfied, executing the conditional cell mobility procedure in the target cell based on the cell configuration parameters of the target cell; maintaining the received initial cell configuration of the at least one candidate target cell upon successful completion of the conditional cell mobility procedure; wherein the steps involved in the process are performed by the communication device.

22. an integrated circuit that, in operation, controls processing of a base station, said processing comprising: - transmitting to the communication device an initial cell configuration for at least one candidate target cell, each initial cell configuration including cell configuration parameters for each candidate target cell and a condition for performing a conditional cell mobility procedure; receiving a notification from a target base station of a target cell of the at least one candidate target cell regarding successful completion of the conditional cell mobility procedure; after receiving the notification regarding successful completion of the conditional cell mobility procedure; - sending a request to one or more of the candidate target cells for which the conditional cell mobility procedure has not been performed, requesting cell configuration parameters for each of the candidate target cells for performing the conditional cell mobility procedure; receiving the requested cell configuration parameters from the one or more candidate target cells; - determining differential cell configuration parameters for each of the candidate target cells, the differential cell configuration parameters comprising cell configuration parameters that differ from cell configuration parameters of the initial cell configuration for each of the candidate target cells; transmitting the differential cell configuration parameters of the one or more candidate target cells to a target base station of the target cell; wherein the steps involved in the process are performed by the base station.

23. an integrated circuit that, in operation, controls processing of a base station, said processing comprising: sending initial cell configuration parameters of the conditional cell mobility procedure to a source base station; performing the conditional cell mobility procedure with the communication device based on the transmitted initial cell configuration parameters; obtaining differential cell configuration parameters of one or more candidate target cells for performing the conditional cell mobility procedure, wherein the differential cell configuration parameters of the candidate target cells include parameters different from initial cell configuration parameters for performing the conditional cell mobility procedure; determining, for each of the one or more candidate target cells, a condition for performing the conditional cell mobility procedure; sending to the communication device a differential cell configuration for each of the one or more candidate target cells, the differential cell configuration including the determined differential cell configuration parameters and the determined execution condition; wherein the steps involved in the process are performed by the base station.

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